LICENSE MANAGEMENT SYSTEM AND METHOD WITH MULTIPLE LICENSE SERVERS

Abstract: A system for managing licenses for protected software on a communication network is disclosed. The system comprises at least one client computer and a pool of license servers coupled to the communication network. The pool of license servers is programmed for managing licenses to use the protected software. Within the pool of license servers is a current leader server, programmed for managing all license servers in the pool, and at least one follower server programmed for managing the distribution of authorizations allocated to that particular follower server. Each license server stores a status of the authorizations allocated to that particular license server, and each follower server communicates the status of the authorizations allocated to that particular follower server to the current leader server. The client computers request authorizations to use the protected software from a particular license server. When a particular license server does not have a sufficient amount of available allocations, the current leader server re-assigns, where possible, the allocations within the pool. The system may also include at least one client computer that is capable of being coupled to or decoupled from the communication network. At least one of the license servers may be programmed for granting a commuter authorization in response to a request for a commuter authorization from a client computer if there is an available authorization. After a commuter authorization is received by a client computer, the client computer stores a commuter authorization lifetime representing a time period for which the commuter authorization is valid. The client computer may then use the protected software while coupled to or decoupled from the communication network until the commuter authorization lifetime expires.

Description: LICENSE MANAGEMENT SYSTEM AND METHOD WITH MULTIPLE LICENSE SERVERS CROSS REFERENCE TO RELATED APPLICATIONS Embodiments of the present invention claim priority from Provisional Application Serial No. 60/152,785, filed September 3, 1999, and are related to U.S. utility patent applications entitled "License Management System And Method With Multiple License Servers", Attorney Docket No. 230074.0227, filed August 25, 2000; "License Management System And Method With License Balancing", Attorney Docket No. 230074.0228, filed August 25, 2000; "System And Method For Selecting A Server In A Multiple Server License Management System", Attorney Docket No. 230074.0229, filed August 25, 2000; and "License Management System And Method For Commuter Licensing", Attorney Docket No. 230074.0230, filed August 25, 2000. The contents of each of these applications are incorporated by reference herein. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates, generally, to license management systems and processes for managing licenses on a computer network and, in preferred embodiments, to such systems and processes involving a pool of license servers for managing software licenses among one or more users on the network, for balancing the management load among the servers in the pool, for selecting a license server to either act as a leader server or from which to seek authorization to run a protected software program, and for granting authorizations to use protected software programs to client computers that may become temporarily disconnected from the network. 2. Description of Related Art The increasing popularity of computer usage in homes and businesses, as well as in governmental, research and education institutions, has brought about a world-wide demand for greater software variety and sophistication. Indeed, the software development industry in most industrialized countries has shown substantial growth in recent years and is expected to show continued growth through the next decade. However, as software sophistication increases, development costs associated with such software also tend to increase. Modern software programs can require months or even years of development, often involving expensive resources and teams of highly skilled engineers and programmers, before a product may be readied for sale or license. Thus, software development companies are often required to make large investments early in the development of their products, in the hope that the products will provide a volume of sales or license revenues sufficient to cover their development investments and generate profits. Illegal software usage and piracy have become a significant problem to software development companies. Because of the nature of computer software, illegal usage and illegal copying of proprietary software programs can be difficult to detect or deter. The increasing usage of computer networks has added to the problem. Computer networks can allow multiple users to access and copy software stored by a common network program server or copy and pass software between each other, over the network. A legitimately purchased or licensed copy of a software program available on a network could result in many illegitimate usages or copies by unauthorized or unlicensed users having access to the network. Various forms of encryption techniques have been developed to inhibit usage of encrypted software by unauthorized users that do not possess a decryption program or key. However, such techniques typically require each authorized users to obtain or be passed a decryption program or key, in advance of usage of the encrypted program. Accordingly, such techniques can be prohibitively inconvenient for some computer and network environments, where it is difficult or impractical to supply each authorized user with a decryption program or key or to decrypt a program for each user or usage. Other software protection techniques have required legitimate or authorized users to have a special hardware device or circuit installed in or plugged into their computer, prior to usage of the protected software. See, e.g., U.S. Patent No. 4,446,519 to Thomas. Again, such techniques can be prohibitively inconvenient for some computer and network environments. For example, if the network environment is such that the authorized user must use multiple computers on the network, then each computer must be provided with the special hardware device. Moreover, if the environment is such that computers having the special hardware device are not located in secure facilities, then unauthorized users may be able to access the protected software by using the non-secure computer in which the special hardware device is installed. Accordingly, more sophisticated license management software has been developed for managing software licenses for computer networks, which do not require encryption of the protected software or special hardware devices in each authorized user's computer. For example, the assignee of the present invention, Rainbow Technologies, Inc. , has marketed versions of a license management system under the trademark, SENTINELLM™. The SENTINELLM™ systems operate with a license server connected to a network of users. The license server stores and manages software licenses for the network users, in accordance with a license management program stored on the server. Each copy of a protected software program on the network is accompanied by a program code corresponding to a shell (also known as "wrapper") or library of Application Program Interface (API) functions, which communicates with the license management program on the server. When a user starts to run the protected software program, the shell code or library of API functions provided with the program communicates a request to use a license to the license server, over the network. The server, under the control of the license management software, responds to the request to determine whether it is storing an available license for the protected software program. If so, the server communicates an authorization message to the user and decrements a count of available licenses stored by the server. If not, the server communicates another message to the user, indicating that no licenses are available. In this manner, licenses are always stored and managed on a network license server. Each network user may have a copy of a protected software program, but must communicate with the license server for authorization to use the protected program. License management systems which employ a license server, as discussed above, provide significant advantages with respect to the freedom to readily add, delete or change authorized users on the network, and the ability to readily control and alter licensing schemes (for example, to add or delete licenses or change conditions for licenses) by modifying only the license server files or programs. However, if all licenses are stored and managed in a single license server, failure of that server can result in a failure of the entire license management system. Accordingly, prior versions of the SENTINELLM™ systems include multiple license server capabilities, wherein two or more license servers are provided on the network, each having a pre-loaded license file and a license management program. One of the servers may be designated as a primary license server, while the others are designated as backup servers. If the primary server cannot be reached by a user, for example, because the primary server has crashed or otherwise gone down, the user may then communicate with a backup server to obtain an authorization message. The backup server, having a pre-loaded copy of the license file and the license management program, may then take over the license management functions. Alternatively, in other prior versions of SENTINELLM™ systems, a shell program or library of API functions could be configured to send a general poll to all servers coupled to the communication channel on which the poll is sent. In response to a general poll, any server computer having a license file containing license information corresponding to the protected software program (whether or not the license information indicated that a license is available) would send a reply to the requesting client computer. The shell program or library of API functions associated with the requesting client computer would then respond to the first reply received from a license server having a license file storing license information for the protected software program. If the replying license server contains an available license for the protected software program, the replying license server provides an authorization message to the requesting client computer. If the replying license server does not contain an available license for the protected software program, the replying license server provides a message to the requesting client computer indicating that authorization to run the protected software program has not been granted. Such a system provides a degree of protection against system failure, in the event that one of the license servers crashes or goes down. The down server computer would not respond to the poll, but other server computers having appropriate license information in their license file would respond to the poll, thus allowing the client computer to continue to seek authorization to run the protected software program, even though one of the servers was down. While the above SENTINELLM™ systems have operated well in many contexts, each license server operates somewhat independent of other license servers. Accordingly, there is a need in the industry for improvements in connection with management and coordination of multiple license servers (or a pool of license servers) in software license management systems for computer networks. SUMMARY OF THE DISCLOSURE Therefore, it is an advantage of embodiments of the present invention to provide a license management system and method for more efficiently managing licenses on a network using a pool of multiple license servers. It is a further advantage of embodiments of the present invention to provide a system and method that facilitates communication between multiple license servers so that any license server in the pool may act as a leader server, should the leader server go down. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network using multiple license servers that allows a client to locate and receive authorization from a new license server, should the old leader server go down. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network using multiple license servers that allows allocations for multiple vendors to be managed with a single process running on a single license server. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network using multiple license servers that allows a redundant license file containing a new hard limit of allocations and a new initial distribution of allocations to be loaded onto one license server and then copied to other license servers in the server pool. It is a further advantage of embodiments of the present invention to provide a license management system and method for managing licenses on a network using multiple license servers that allows allocations to be distributed among the license servers and then re-assigned between license servers by updating the distribution tables of the license servers to facilitate a dynamic balancing of allocations among license servers based on actual or expected usage. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network using multiple license servers that allows allocations to be re-assigned from a nonfunctional (down) license server to a functioning license server by updating the distribution table of the functioning license server to facilitate a dynamic balancing of allocations among license servers based on actual or expected usage. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network using multiple license servers that allows a network administrator to change the initial distribution of allocations, add allocations, or add license codes for protected software. It is a further advantage of embodiments of the present invention to provide a license management system and method for managing licenses on a network using multiple license servers that allows a particular license server on a particular subnet to be selected by the network administrator to operate as the leader server due to its physical location, speed, or efficiency. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network using multiple license servers that allows a client computer to determine which is the best license server from which to seek authorization to run the protected software program, thereby balancing the license management load such that the number of available allocations (for a given protected software program, feature or version) can be adjusted to achieve an optimal distribution for each license server in the pool. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network that allows a client computer to request and receive a commuter authorization from a license server while connected to the network, allowing the client computer to run a protected software program even if the client computer should become disconnected from the network. It is a further advantage of embodiments of the present invention to provide a system and method for managing licenses on a network that allows a client computer to request and receive a commuter authorization from a license server while disconnected from the network, allowing the client computer to run a protected software program while disconnected from the network. These and other advantages are accomplished according to a system for managing licenses for protected software on a communication network. The system comprises at least one client computer and a pool of license servers coupled to the communication network. The pool of license servers is programmed for managing licenses to use the protected software. Within the pool of license servers is a current leader server, programmed for managing all license servers in the pool, and at least one follower server programmed for managing the distribution of authorizations allocated to that particular follower server. The first license server to be started is selected as the current leader server. However, if no license server is started first, the license server with the highest priority, as determined by a leader priority list, is selected as the current leader server. Each follower server is capable of becoming a new leader server if the current leader server can no longer manage the distribution of authorizations for the license servers. Each license server stores a status of the authorizations allocated to that particular license server, and each follower server communicates the status of the authorizations allocated to that particular follower server to the current leader server. The client computers request authorizations to use the protected software from a particular license server. When a particular license server does not have a sufficient amount of available allocations, the current leader server re-assigns, where possible, the allocations within the pool by updating the distribution tables of license servers in the pool, to give at least one additional allocation to the particular license server. In addition, client computers seeking authorization to use the protected software may receive information from the server pool and select a particular license server from which to request authorization based on the received information. The system may also include at least one client computer that is capable of being coupled to or decoupled from the communication network. While coupled to the communication network, a user of the client computer may request a commuter authorization to use the protected software. At least one of the license servers may be programmed for granting a commuter authorization in response to a request for a commuter authorization from a client computer if there is an available authorization. After a commuter authorization is received by a client computer, the client computer stores a commuter authorization lifetime representing a time period for which the commuter authorization is valid. The client computer may then use the protected software while coupled to or decoupled from the communication network until the commuter authorization lifetime expires. These and other objects, features, and advantages of embodiments of the invention will be apparent to those skilled in the art from the following detailed description of embodiments of the invention, when read with the drawings and appended claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a generalized block diagram representation of an example network environment according to an embodiment of the present invention. FIG. 2 is a generalized representation of a redundant license file (RLF) for the network environment of FIG. 1 according to an embodiment of the present invention. FIG. 3 is a generalized representation of a license code contained in an RLF of FIG. 2 according to an embodiment of the present invention. FIG. 4 is a generalized representation of a license code contained in an RLF and copied into a license table and a distribution table within a single license server for the network environment of FIG. 1 according to an embodiment of the present invention. FIG. 5 is a generalized representation of an initial state of the distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers according to an embodiment of the present invention. FIG. 6 is a generalized representation of the distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 5 after an authorization has been granted by follower server B according to an embodiment of the present invention. FIG. 7 is a generalized representation of the distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 6 after an authorization has been granted by follower server C according to an embodiment of the present invention. FIG. 8 is a generalized representation of the distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 7 after an authorization has been granted by leader server A according to an embodiment of the present invention. FIG. 9 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 8 after old leader server A has gone down and follower server B has been elected as the new leader server according to an embodiment of the present invention. FIG. 10 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 9 after a client who formerly received an authorization from old leader server A has now received an authorization from new leader server B according to an embodiment of the present invention. FIG. 11 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 10 after old leader server A has come back on line as a follower server according to an embodiment of the present invention. FIG. 12 is a generalized representation of a license code contained in an RLF and copied into a license table and a distribution table within a single license server for the network environment of FIG. 1 according to an embodiment of the present invention. FIG. 13 is a generalized representation of an initial state of distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers according to an embodiment of the present invention. FIG. 14 is a generalized representation of distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 13 after an authorization has been granted by follower server B according to an embodiment of the present invention. FIG. 15 is a generalized representation of distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 13 after 28 authorizations have been granted by follower server B according to an embodiment of the present invention. FIG. 16 is a generalized representation of distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 15 after client computer B has requested an authorization from follower server B, one allocation has been re-assigned to follower server B from leader server A, and one allocation has been re-assigned to follower server B from the free pool according to an embodiment of the present invention. FIG. 17 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 16, after one additional authorization has been granted by leader server A according to an embodiment of the present invention. FIG. 18 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 17, after leader server A has gone down and new leader server B has received information on the allocations within all license servers in the server pool according to an embodiment of the present invention. FIG. 19 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 18, after an authorization has been granted to client computer A by new leader server B in response to a heartbeat from client computer A in fail-over mode according to an embodiment of the present invention. FIG. 20 is a generalized representation of the distribution tables of license servers A, B and C in a server pool comprising three license servers in the example of FIG. 18, after new leader server B has re-assigned an available allocation from old leader server A to new leader server B by updating the distribution table of new leader server B according to an embodiment of the present invention. FIG. 21 is a generalized block diagram representation of an example network environment illustrating the storing of commuter authorization information according to an embodiment of the present invention. FIG. 22 is a generalized representation of the distribution tables of leader server A and follower servers B and C in a server pool comprising three license servers in the example of FIG. 14 after a commuter authorization has been granted by follower server C according to an embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In the following description of preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the preferred embodiments of the present invention. Preferred embodiments of the invention relate to a system and process involving a pool of license servers for managing licenses to, for example, one or more protected software programs, files or other data structures, among one or more users on the network. Protected software may include, but is not limited to, for example, a software program, such as a word-processing program, a graphics program, a computer game, etc., a proprietary file or other data structure, such as a data-base or other form of data, as well as other software encoded information or instructions, for which the control of user access is desired. For purposes of simplifying the present disclosure, the protected software used in the following examples is one or more proprietary software programs. System architecture According to a preferred embodiment of the present invention, the plurality of license servers are managed in accordance with a server pool scheme, as controlled by a license management program associated with each license server computer and the shell program or library of API functions associated with each copy of the protected software program. In preferred embodiments, the pool of license servers comprises three to 11 servers. However, it should be noted that alternative embodiments of the present invention are not limited to any particular maximum number of license servers. In addition, in further alternative embodiments, multiple pools of license servers can reside on a single network. In further alternative embodiments only a single license server is required for issuing commuter authorizations. However, for purposes of illustration only, embodiments of the present invention will be described herein with reference to a pool of three license servers. An example hardware environment for an embodiment of the present invention is illustrated, generally, in FIG. 1. With reference to FIG. 1, a computer network 10 includes a plurality of user or client computers 12 and three license servers 14, each coupled for communication over a communication network link, generally referenced at 16. The plurality of client computers 12 are identified as "Client 1", "Client 2", and "Client N", and the plurality of license servers 14 are labeled as "Lie. Server A", "Lie. Server B", and "Lie. Server C." Embodiments may employ any suitable number of client computers 12 and any suitable number of license servers 14. Also, while not shown in FIG. 1, the network 10 may include additional components, including one or more program or file servers, routers and/or other well known network devices and resources. Each client computer 12 preferably includes a suitable processor and associated transient memory, such as an RAM, for running a protected software program. The client computer may be part of a standard personal computer (PC), network terminal, workstation or the like. In one preferred embodiment, each client computer 12 is coupled to a persistent program storage memory device 18, which may include, but is not limited to, a hard disc drive, floppy disc drive, tape drive, CD-ROM or the like, having a computer readable medium on which the protected software program is stored. Also stored as part of the protected software program is additional program code, such as code corresponding to a shell or library of API functions as discussed above, for communicating with the license servers which are under control of a license management program, in accordance with communication functions discussed below. Each license server 14 preferably includes a suitable processor and associated transient memory, such as an RAM, for running a license management program as described herein. In addition, each license server 14 is coupled to one or more persistent program storage memory devices 20, which may include, but is not limited to, a hard disc drive, floppy disc drive, tape drive, CD-ROM or the like, having a computer readable medium on which a license management program 22 and a redundant license file (RLF) 24 are stored. Redundant license files An example embodiment of an RLF 24 is shown in FIG. 2 as containing license codes 26 for proprietary software programs A, B, C, etc. Each license code 26, in one example embodiment, comprises a string of data relating to license policy and the software program to which the license policy applies. In preferred embodiments, license codes 26 for software produced by more than one vendor can reside within the same RLF 24 of the same license server 14, and may be managed with a single process (execution of the license management software) running on a single license server 14. Thus, any given licenser server 14 does not need to have multiple license management processes running to manage licenses for multiple protected vendor applications. Instead, only one license management program needs to be running on a given license server 14, to manage licenses for protected vendor applications managed by that license server. In the example embodiment of FIG. 3, a license code 26 comprises a data string defining multiple records or fields Rl, R2, R3 ... RN, wherein each record corresponds to an attribute associated with the license policy, the software program to which the license policy applies, or other information. In preferred embodiments, each license code 26 includes at least one attribute associated with a license policy, the number of allocations for using the protected software program, and at least one other attribute associated with the identity of the protected software program. The number of allocations for using the protected software program is the maximum number of users that can be running the protected software program at any one time, and is also referred to as the ceiling or hard limit. In preferred embodiments, license code 26 also includes a flag which determines if commuter licensing functionality, described herein, is enabled or disabled for the corresponding protected software program. This flag allows the software developer to make commuter licensing available only to selected customers. Data associated with a license policy preferably includes data representing the expiration date or expiration time of the license, as granted by the licensee (e.g., the protected software program's owner or developer). For purposes of illustration only, in the embodiment of FIG. 4 only one fictional license code 26, identified as "Application vl.O," is stored in the RLF 24 of a license server 14, with a hard limit of 100 total allocations distributable across all license servers 14 (see reference character 28). In preferred embodiments, another attribute of the RLF 24 is the IP address 32 for each license server 26. Another attribute of the RLF 24 is the distribution of the 100 allocations across all the license servers 14. This distribution is identified as the initial distribution 30, and is configurable by the network administrator. In the example of FIG. 4, an initial distribution 30 of A:40, B:30, C:30, indicates that 40 allocations will initially be assigned to license server A, 30 allocations will initially be assigned to license server B, and 30 allocations will initially be assigned to license server C. This initial distribution 30 also signifies that the pool will comprise three license servers. If the network administrator makes an initial distribution that does not equal the hard limit of allocations (see reference character 28), in preferred embodiments of the present invention the extra allocations will be put into a free pool 48 maintained within the distribution table 36. If, on the other hand, the network administrator makes no initial distribution 30 of allocations in the RLF 24, preferred embodiments will divide the allocations evenly over the number of servers in the pool, and any extras will be put in the free pool 48. For example (but not illustrated in FIG. 4), if no initial distribution 30 was assigned by the network administrator, information representing an even distribution of A: 33, B:33, and C:33 would be stored in the initial distribution attribute 30 of the RLF 24, and when a particular license server 14 is started, the RLF 24 would load an even distribution of A:33, B:33, and C:33 into the current distribution attribute 40 of distribution table 36, and would load a value of one into the free pool 48. In preferred embodiments of the present invention, each RLF 24 stored in each license server 14 is an exact copy of every other RLF 24 of license servers in the pool. Thus, attributes of the license code 26 such as the expiration date or number of allocations need not be passed between license servers 14 in response to a request for authorization to use a protected software program from a client computer 12, because an exact copy of the license code 26 has already been stored on the hard disk of each license server 14 prior to the startup of that license server 14. Each license server 14 operates, under the control of its associated license management program 22, to perform license management functions in association with data contained in the RLF 24, as described herein. Thus, when a particular license server 14 is started, the license server 14 loads the contents of its RLF 24 into a license table 34 in RAM or other memory and reads the license table 34, which identifies that server as a license server 14. It should be noted that in preferred embodiments, the license table 34 is never modified. In addition, the contents of the RLF 24 is loaded into a distribution table 36 in RAM or other memory, and the initial distribution 30 is further copied into another record, distinct from the license code 26, identified as a current distribution 40. Unlike the license table 34, the distribution table 36 changes its current distribution 40 over time to keep track of current allocations. Selection of a leader server at start-up In preferred embodiments of the present invention, when the license servers 14 in the server pool are first started up, the first license server 14 to come on line is designated as a leader server. The leader server always has a global picture of the current distribution of allocations within every license server 14 in the server pool. If none of the license servers 14 were definitively started first, the license server 14 having a higher priority as established by a leader priority list will be designated the leader server. The leader priority list is stored in the RLF 24 and is read at the time of server startup. This is known as a leader election process. All other license servers 14 are designated as follower servers. The ability to intentionally start up a particular license server 14 and force it to be the leader server is advantageous because it may be desirable for a particular license server 14 on a particular subnet to operate as the leader server due to its physical location, speed, or efficiency. In prior art systems, the leader server always had the highest IP address, and to change leader servers required physically reconnecting to a different address or reconfiguring the license servers by changing the IP address. In embodiments of the present invention, however, the leader server may be changed simply by turning a particular license server 14 on first. License management — issuance of authorizations For purposes of illustration only, FIG. 5 illustrates an example of the distribution tables 36 for a three server pool consisting of license servers A, B, and C. Assume, for this illustration, that all three license servers have been started up, and that license server A has been designated as the leader server, and B and C as the follower servers. Further assume that the hard limit of allocations for the software program Application vl.O is 100, as indicated by the hard limit record 28 associated with the license code 26 for Application vl.O within each distribution table 36. In addition, assume that the current distribution of allocations is 40 on leader server A, 30 on follower server B, and 30 on follower server C, as indicated in the current distribution record 40 associated with the license code 26 for Application vl.O within each distribution table 36. Note also that in the embodiment of FIG. 5, associated with each license code 26 is a record for available allocations for each server in the pool (see reference character 38), a record for available allocations for all servers in the pool (see reference character 44), and a record for allocations currently in use for each server in the pool (see reference character 42). The allocations in these records are values which are incremented or decremented as authorizations are issued, returned, or borrowed. It should be understood that the records identified by reference characters 28, 38, 40, 42, and 44 in FIG. 5 are associated with a particular license code 26, but are distinct from it. As indicated in FIG. 5, in preferred embodiments of the present invention the structure of the distribution tables 36 will be the same for both the leader server A and follower servers B and C, but only the distribution table 36 for leader server A (the leader distribution table) will reflect the allocation status of the other license servers 14 in the server pool. In contrast, the distribution tables 36 for follower servers B and C (the follower distribution tables) will only reflect the allocation status of that particular follower server, as indicated by the X (don't care) designations in portions of the follower distribution tables. When a user at a client computer 12 desires to run Application vl.O from a follower server, such as follower server B, for example, the client computer 12 may first load some or all of the protected program into the transient memory of the client computer 12, along with the program code corresponding to a shell or library of API functions. Alternatively, the protected program may remain in persistent memory 18 until and unless the server computer communicates an authorization signal to the shell program or library of API functions. Loading of the shell program or library of API functions is preferably transparent to the user on the client computer 12 and, preferably, occurs in response to the user inputting a command to open the protected software (for example, by clicking a mouse button on an icon associated with the protected software). As part of the function of the shell or library of API functions, a request is then sent from the client computer 12 to follower server B for one or more authorizations to run the protected program. For purposes of this example, assume that client computer 12 requested only one authorization. Follower server B, under the control of the license management software, responds to the request by looking at its distribution table 36 to determine whether it has available allocations for Application vl.O. In the example of FIG. 5, follower server B has 30 allocations available, as represented by the allocations available record for each server in the pool (reference character 38) in the distribution table 36 for follower server B. Because it has available allocations, follower server B communicates an authorization message to the client computer 12. As illustrated in FIG. 6, once the authorization message is sent, the distribution table 36 is updated so that the available allocations record 38 for follower server B decreases to 29, and the allocations in use record 42 for follower server B increases to one. If an insufficient number of allocations are available to completely satisfy the request, no authorizations are sent, and follower server B communicates another message back to the client computer 12, denying the request. In preferred embodiments, follower server B will then issue a borrow request in an attempt to borrow available allocations from another source. As noted above, in preferred embodiments of the present invention the leader server always has a global picture of the distribution of allocations in the whole server pool. Thus, in the present example any changes to the distribution table of follower server B must be communicated to leader server A. In preferred embodiments, follower server B can determine the IP address for the leader server A from a leader priority list 46, which is configurable by the network administrator. It should be noted that in preferred embodiments, the IP address of all license servers in the server pool are stored in the leader priority list 46, a data structure separate from the license codes 26, to facilitate faster lookup. However, in alternative embodiments the IP addresses may be stored in a record associated with the license codes 26. In any case, after determining the IP address of the leader server A, follower server B communicates the fact that its available allocations count has dropped to 29 to leader server A, and the distribution table of leader server A will be updated accordingly. Thus, as illustrated in FIG. 6, the distribution table 36 of leader server A reflects that the allocations available record 38 for follower server B has dropped to 29, the allocations in use record 42 for follower server B has increased to 1 , and that the record for allocations available for all servers in the pool (see reference character 44) has dropped to 99. Similarly, if another client computer 12 requests authorization to run Application vl.O from follower server C, follower server C will look at its distribution table 36, determine that it has 30 allocations available, and send an authorization back to the client computer 12. As illustrated in FIG. 7, once the authorization is sent, the allocations available record 38 for follower server C drops to 29, and the allocations in use record 42 for follower server C increases to one. This change is then communicated to leader server A, whose distribution table 36 will reflect that the allocations available record 38 for follower server C has dropped to 29, the allocations in use record 42 for follower server C has increased to one, and that the record for available allocations for all servers in the pool (see reference character 44) has dropped to 98. It should be noted in FIG. 7 that the distribution tables 36 for follower servers B and C keep track of changes to their own allocations, but do not keep track of changes to the allocations of other license servers. License balancing -- selection of a license server by a client computer In accordance with a further aspect of a preferred server pool embodiment, a client computer 12 seeking authorization to run a protected software program may first locate a plurality of license servers 14 on the network, and more preferably, locate all license servers 14 on the network. This may be accomplished with a general poll to all license servers 14 in the server pool. In response to the poll, each license server 14 provides the client computer 12 with information about that particular license server 14. Such information may be included in a reply message or in a subsequent message sent from each license server 14 to the client computer 12. Alternatively, each license server's reply may be merely the identity of the replying license server 14, wherein the client computer 12 employs the identity information received for each license server 14 as a key to a look-up table or database (not shown) to locate other information about each license server 14, such as, but not limited to, the license server's protocol support, the total number of client computers 12 currently connected to the license server 14, IP address, and the number of available allocations for a given protected software program. The lookup table or database may be stored in a persistent memory 18 associated with the client computer 12 or may be stored in other memory (not shown) accessible to the client computer 12 over the network 16. With the license server information corresponding to a plurality of license servers 14 from which replies were received, the client computer 12, under the control of the shell program or library of API functions, determines which is the best license server 14 from which to seek authorization to run the protected software program. In preferred embodiments, the client computer 12 renders this determination based on a number of license server characteristics, such as, but not limited to: protocol support, the total number of client computers 12 currently connected to the license server 14, IP address, and the number of available allocations for a given protected software program. Other factors may also be used in the determination, such as the location of the license servers 14 relative to the requesting client computer 12. In an alternative embodiment, the server computers 14 in the server pool determine which license server 14 is the best license server 14 for the request, for example, based on the above-noted characteristics or other factors. By using information such as the total number of client computers 12 connected to each license server 14 and the number of available allocations in each license server 14 as part of the determination of which license server 14 is the best license server 14 to handle the request, the license management load can be balanced such that the number of available allocations (for a given protected software program, feature or version) can be adjusted to achieve an optimal amount for each license server 14 in the pool. Thus, for example, the determination of which license server 14 will handle a client computer's request to run a particular protected software program may be based, in whole or in part, on which license server 14 has the most available allocations. Alternatively, the determination may be based, in whole or in part, on a scheme which tends toward maintaining an equal number of available allocations in each active license server 14 in the pool, wherein license servers 14 having a higher than average or mean number of available allocations are favored over other license servers 14 in the pool. Yet a further alternative, the determination may be based on a scheme having a tendency to maintain a larger number of available allocations at license servers 14 that are expected to receive a higher volume of requests for authorization to run the particular protected software program, relative to other license servers 14 in the pool, for example, by favoring such other license servers 14 in the determination. Selection of a new leader server when the current leader server goes down In embodiments of the present invention, the license servers 14 periodically communicate with (ping) each other so that the license servers 14 know which other license servers 14 are down or up. The communication, or pinging, may be in the form of a periodic signal (heartbeat) sent from the leader server to the follower servers. Server identification information, such as the IP address of the follower server, may be contained within this heartbeat, but license code information need not be communicated. If the leader server does not receive an acknowledgement (ack) from a particular follower server in response to the heartbeat within an expected period of time, the leader server will designate that follower server as being down. In addition, if a follower server does not receive a heartbeat from the leader server within an expected period of time, it sends a leader check message to the leader server to check if the leader server is still alive. If the leader server is alive, it will send an "ack" in response to the leader check message. If no "ack" is received, the follower server will start a leader election process to select a new leader server. In preferred embodiments, the preference order contained in leader priority list 46 is traversed until a functioning follower server with the highest priority is located. This follower server then becomes the new leader server. In alternative embodiments, the functioning follower server with the highest IP address is elected as the new leader server. In communications from leader to follower servers, each message contains updated server status (up/down) for each server in the pool. When a follower server receives a message from the leader server, the follower server updates its server status information, which is used when initiating the leader election process. It should be understood that follower servers do not ping each other to check if each other is alive, because that would generate unnecessary network traffic. Thus, the follower servers rely on status information passed to them by the leader server. In preferred embodiments of the present invention, if the leader server sends acknowledgement heartbeats to the followers, and one of the follower servers (B, for example) receives the acknowledgement but follower server C does not, only follower server C will send one or more re-try heartbeats. If follower server C still does not receive an acknowledgement to the re-try heartbeats, follower server C will communicate with follower server B and attempt to initiate a process to select a new leader server. However, follower server B has already received an acknowledgement from leader server A, so follower server B will communicate with leader server A and inform leader server A that follower server C is initiating a process to select a new leader server. At this time, leader server A will send a new heartbeat to follower server C. If leader server A fails to receive a reply heartbeat from follower server C, and follower server C again contacts follower server B about a process to select a new leader, then follower server B will communicate to follower server C that a leader server already exists in the server pool. At that point, follower server C will disassociate itself from the pool. Fail-over mode Continuing the example of FIG. 7 for purposes of illustration only, assume that a client computer A has requested and received an authorization to run Application vl.O from leader server A. As illustrated in FIG. 8, once the authorization is sent, the allocations available record 38 for leader server A drops to 39, the allocations in use record 42 for leader server A increases to one, and that the record for available allocations for all servers in the pool (see reference character 44) has dropped to 97. Thus, at this point in time, one client computer 12 is connected with each license server 14. Now assume that leader server A goes down. Because the license servers 14 are periodically pinging each other, the two follower servers B and C will soon determine that leader server A has gone down. Further assume that follower server B is then selected as the new leader server. New leader server B will already have its own RLF 24, license table 34, and distribution table 36, which includes the current distribution of allocations 40. However, new leader server B does not have the global allocation information maintained by the old leader server A. Therefore, upon becoming the new leader server, license server B must now receive this information from the other license servers. As illustrated in FIG. 9, because license server A is now down, within the distribution table 36 for new leader server B, the allocations in use record for license server A (see reference character 42) is set to zero, and the allocations available record (see reference character 38) is set to 40. When new leader server B sends a heartbeat to follower server C, the heartbeat contains information which identifies B as the leader server. Follower server C will send an "ack" in response to the heartbeat from new leader server B, and in the process, will provide information on the allocations in use record and allocations available record for follower server C. Once this information is received, within the distribution table 36 for new leader server B, the allocations in use record for license server C (see reference character 42) is set to one, and the allocations available record (see reference character 38) is set to 29. In addition, the record for available allocations for all servers in the pool (see reference character 44) is set to 98. In this manner, new leader server B receives a global picture of the status of the license servers in the server pool. Meanwhile, because client computers 12 connected to a particular license server 14 are also periodically communicating with each other, for example, using a regular heartbeat function that indicates that each is still functioning, client computer A will soon determine that server A went down. Client computer A knows that it has received an authorization to run the protected program from server A, and therefore knows that it must enter a fail-over mode and look for a new license server 14 from which to receive an authorization. Because client computer A receives leader priority list 46 from a license server 14 whenever client computer A receives an authorization, client computer A knows the IP address of every license server 14 in the server pool. Client computer A then sends a heartbeat to the remaining license servers 14 in turn, in the order designated in leader priority list 46, until it finds a server (B, in this example) with an available allocation. In preferred embodiments of the present invention, each license server 14 maintains a key table containing a list of client computers 12 that currently have authorizations issued by that license server 14. Thus, in the present example, when new leader server B receives a heartbeat from client computer A, new leader server B will determine from the key table that it did not previously issue an authorization to client computer A. Thus, new leader server B will convert the heartbeat to a request, and will reserve the requested number of allocations for client computer A, provided it has the requested number of allocations available. In this manner, as client computers 12 formerly connected to old leader server A locate and ping new leader server B, new leader server B will issue authorizations and accept the allocations of old leader server A. The distribution table 36 of new leader server B will then change accordingly. As illustrated in FIG. 10, once client computer A is authorized by new leader server B, the distribution table for new leader server B will be updated such that the allocations in use record (see reference character 42) for leader server B is increased to two, and the allocations available record (see reference character 38) is decreased to 28. If client computer A, in fail-over mode, sends a heartbeat to new leader server B, but new leader server B doesn't have an available allocation, then new leader server B will send a denial message to client computer A. It should be noted that new leader server B may also seek to re-allocate or borrow an allocation from another license server. In response to the denial message, client computer A will send its next heartbeat to the next license server 14 in the key table (follower server C in this example). If follower server C has an available allocation, it will convert the heartbeat to a request, and issue an authorization to client computer A. In accordance with a further aspect of a preferred server pool embodiment, a client computer 12 in fail-over mode seeking authorization to run a protected software program may first locate a plurality of remaining functioning license servers 14 on the network, and more preferably, locate all remaining functioning license servers 14 on the network, rather than sending a heartbeat to the remaining functional license servers 14 in the order determined by the leader priority list. The location of all remaining functioning license servers 14 may be accomplished with a general poll to all license servers 14 in the server pool. In a manner similar to the selection of an optimal license server 14 by a client computer 12 seeking to obtain an authorization, the client computer 12 in fail-over mode may then select an optimal license server 14 after receiving information from all functioning license servers 14 in response to the general poll. Network administrator modifications to the redundant license file If old leader server A should come back up, it will be a follower server, and have an initial distribution according to the allocations for old leader server A in the distribution table of new leader server B, regardless of what is contained in the RLF 24. Old leader server A can become the leader server again, if new leader server B goes down. When old leader server A comes back up as follower server A, follower server A sends a heartbeat to new leader server B, who then recognizes that follower server A is back up. New leader server B then transmits the current allocation of old leader server A to follower server A. Continuing the example of FIG. 10 for purposes of illustration only, if old leader server A comes back up as follower server A, the current allocation of old leader server A (see reference characters 42 and 38) in the distribution table 26 of new leader server B, which is zero allocations in use, 40 available, will be communicated to follower server A. This allocation is reflected in the distribution table 26 of follower server A in FIG. 11. In alternative embodiments of the present invention, before bringing old leader server A back up as follower server A, the network administrator may use this opportunity to modify the RLF 24. Modification of the RLF 24 may be desirable because a new license code 26 was added, or because a modification of the initial distribution of allocations 30 for a given license code 26 already in the RLF 24 is desired. In preferred embodiments of the present invention, each RLF 24 has an associated sequence or version number. Each time the RLF 24 is changed, the sequence number is incremented. Thus, if license servers should have RLFs 24 different sequence numbers, some RLFs 24 are not up to date. Continuing the example above for purposes of illustration only, when old leader server A comes back up as follower server A with a new RLF 24, it sends a "server up" message which includes the sequence number of its RLF 24 to the other license servers 14. When the other license servers B and C respond to follower server A's "server up" message, license servers B and C will send a reply back to follower server A which includes their own sequence numbers. When follower server A receives these replies, it compares the sequence numbers. In the present example, follower server A will determine that it has the highest sequence number, indicating that follower server A has the latest RLF 24. Follower server A will then send a message to new leader server B indicating that follower server A has the latest RLF 24. New leader server B will then acknowledge this message and goes into a receive mode, at which time follower server A copies the RLF 24 to new leader server B. Once new leader server B has received a copy of the latest RLF 24, new leader server B notifies other functioning follower servers that it has a new RLF 24, and the new RLF 24 is then copied to the other functioning follower servers. In the preferred embodiment described above, the leader server is updated with the new RLF 24 before any other license server 14 in the pool, because, at any point in time, the leader server should have the correct and the latest information. After the license servers 14 receive the new RLF 24, their license tables 34 and distribution tables 36 are updated based on the new RLF 24. The process described above is advantageous in that it allows a network administrator to update the RLF 24 on each license server 14 without taking each license server 14 off line, loading the new RLF 24, and then bringing it back up. Instead, the RLF 14 for license servers 14 in the server pool can be updated by bringing only one license server 14 down. In alternative embodiments of the present invention, the RLF 24 may be updated without the necessity for bringing a license server 14 down. In such embodiments, the network administrator would initiate a utility from a client computer 12 that sends an "update RLF" message containing a new RLF 24 to a particular license server 14. The particular license server 14 would then proceed as described above. It should be noted that in embodiments of the present invention, a network administrator can also use this process to add a license server to the pool by simply bringing the new license server 14 on line. When the new license server is brought on line, it may have a new RLF 24. Majority rule In addition to the purposes described above, the heartbeats communicated between the follower servers and the leader server are also used to enforce majority rule. Majority rule is a security measure to prevent excessive authorizations from being issued. License servers 14 operating under majority rule will only issue an authorization if a majority of license servers 14 in the server pool are up and running. Continuing the example server pool described herein for purpose of illustration only, suppose the two follower servers B and C go down. Because of the communication between license servers 14, leader server A will know that only one license server - itself — is still operating. Leader server A will also check a key file, which stores the total number of license servers 14 in the server pool, and note that the key file stores a value of three. Although leader server A is still up and running, because there is no majority of license servers running (only one of the three license servers are running), leader server A is precluded by the majority rule from issuing authorizations. Without the majority rule, which may be ignored in alternative embodiments of the present invention, the network could be intentionally segmented such that each license server 14 becomes isolated from every other license server 14. With the license servers 14 isolated, each license server 14 would appear to be the only license server 14 in the server pool, and thus would operate as a leader server. It would then be possible to receive authorizations from each of these independent leader servers for all allocations, for a total of three times as many allocations for each legitimate license. Dynamic license balancing — borrowing Referring to a new example illustrated in FIG. 12 for purposes of illustration only, only one fictional license code 26, identified as "Application vl.O," is stored in the RLF 24 of a license server 14, with a hard limit of 100 total allocations distributable across all license servers 14 (see reference character 28). In the example of FIG. 12, an initial distribution 30 of A:39, B:30, C:30, indicates that 39 allocations will initially be assigned to license server A, 30 allocations will initially be assigned to license server B, and 30 allocations will initially be assigned to license server C. It should be noted that in the example of FIG. 12, only 99 of the 100 allocations have been initially assigned by the network administrator. Thus, in the example of FIG. 12, one allocation is put into free pool 48. Continuing the example of FIG. 12, assume that a request is sent from a client computer 12 to follower server B for one or more authorizations to run the protected program. For purposes of this example, assume that client computer 12 requested only one authorization. Follower server B, under the control of the license management software, responds to the request by looking at its distribution table 36 to determine whether it has available allocations for Application vl.O. In the example of FIG. 13, follower server B has 30 allocations available, as represented by the available allocations record for each server in the pool (reference character 38) in the distribution table 36 for follower server B. Because it has available allocations, follower server B communicates an authorization message to the client computer 12. As illustrated in FIG. 14, once the authorization message is sent, the distribution table 36 is updated so that the available allocations record 38 for follower server B decreases to 29, and the allocations in use record 42 for follower server B increases to one. Follower server B will then communicate the fact that its available allocations count has dropped to 29 to leader server A, and the distribution table of leader server A will be updated accordingly. Thus, as illustrated in FIG. 14, the distribution table 36 of leader server A reflects that the available allocations record 38 for follower server B has dropped to 29, the allocations in use record 42 for follower server B has increased to 1 , and that the record for allocations available for all servers in the pool (see reference character 44) has dropped to 99. Dynamic license balancing will be described next according to embodiments of the present invention. In preferred embodiments, license server 14 stores a value for a borrowing threshold that can be set, for example, by the network administrator. Fundamentally, the borrowing threshold is an indicator that the number of available allocations for a particular protected software program assigned to a particular license server 14 has reached an unacceptably low level. The network administrator can independently set the borrowing threshold for each license server 14 such that borrowing, or license balancing, may be enabled when a certain percentage of the allocations assigned to a particular license server 14 are in use. In preferred embodiments of the present invention the borrowing threshold can be set to a value of between 1 % and 90% . However, in alternative embodiments, the borrowing threshold can be set to as high as 100% . Generally, any time the borrowing threshold is exceeded, a borrow request to the leader server will be initiated. Continuing the example of FIG. 14 for purposes of illustration only, assume that the borrowing threshold has been set to 90% , and a cluster of client computers 12 have requested 27 more authorizations for Application vl.O from follower server B. As illustrated in FIG. 15, once the authorization messages have been sent by follower server B, the available allocations record 38 for follower server B decreases to two, and the allocations in use record 42 for follower server B increases to 28. This change is then communicated to leader server A, whose distribution table 36 will reflect that the available allocations record 38 for follower server B has decreased to two, the allocations in use record 42 for follower server B has increased to 28, and that the record for allocations available for all servers in the pool (see reference character 44) has decreased to 72. It should be noted in FIG. 15 that the distribution tables 36 for follower servers B and C keep track of changes to their own allocations, but do not keep track of changes to the allocations of other license servers. At this point in time, greater than 90% of the allocations for follower server B are in use. Because the borrowing threshold of 90% has been exceeded, follower server B will then initiate a borrow request. In preferred embodiments of the present invention, borrowing always occurs through the leader server because the leader server always maintains a complete picture of the current distribution of allocations within the server pool. However, before a borrow request can be processed, the number of allocations to be borrowed must be determined. In preferred embodiments, the number of allocations to be borrowed is dependent on (1) the number of allocations needed to drop below the borrowing threshold, and (2) the borrowing threshold itself. Generally, the number of allocations to be borrowed is equivalent to the number of allocations needed to drop below the borrowing threshold, plus a number of extra allocations inversely related to the borrowing threshold. If the borrowing threshold is generally lower, it may be exceeded more frequently, and thus the number of extra allocations is set higher. If the borrowing threshold is generally higher, it may be exceeded less frequently, and thus the number of extra allocations is set lower. In the example of FIG. 15, follower server B will determine that, with 28 allocations in use, two available allocations are needed to drop below the borrowing threshold. (If only one available allocation was borrowed, for a total allocation of 31, then 28 ÷ 31 = 90.3% , which still exceeds the borrowing threshold of 90% . However, if two available allocations are borrowed, for a total allocation of 32, then 28 ÷ 32 = 87.5% , and the borrowing threshold is not exceeded.) Moreover, because the borrowing threshold of 90% is relatively high and may be exceeded less frequently, no extra allocations will be borrowed. Thus, in the example of FIG. 15, assume that a total of two allocations will be borrowed. When leader server A receives the borrow request from follower server B, in preferred embodiments of the present invention leader server A looks within its own memory — first at the free pool 48, then to the allocation of any down license servers, and finally to its own current allocation ~ to locate an available allocation. However, in alternative embodiments, other sequences may be employed. In the example of FIG. 15, leader server A will determine that one allocation is available from the free pool 48, no license servers 14 are down, and that one allocation is available from the current allocation of leader server A. Leader server A will then borrow (re-assign) one allocation each from free pool 48 and leader server A to follower server B. As illustrated in FIG. 16, after the borrowing has occurred, the distribution table 36 for leader server A will reflect the re-assignment of allocations caused by the borrowing. In the distribution table for leader server A, the current distribution 40 of leader server A has changed to A:38, B:32, C:30, the available allocations record 38 for follower server B has increased to four, and the free pool 48 for leader server A has decreased to zero. In preferred embodiments of the present invention, after the distribution table 36 for leader server A has been updated, leader server A sends a distribution criteria sync message to follower servers B and C to change their distribution tables 36. As illustrated in FIG. 16, after the distribution criteria sync message has been received by follower servers B and C, the distribution table 36 for follower server B reflects the new current distribution 40 of A:38, B:32, C:30, and a new available allocations record 38 of four. The distribution table 36 for follower server C also reflects the new current distribution 40 of A:38, B:32, C:30. It should be noted that even though a successful borrow request will change the assignment of allocations within the server pool, the initial distribution 30 in the RLFs 24 and license tables 34 (see FIG. 12) do not change. In the example of FIG. 15, the leader server A was able to borrow (reassign) one allocation each from free pool 48 and leader server A to follower server B. However, if an insufficient number of available allocations were available from free pool 48 and leader server A, leader server A will send a borrow request to follower server C on behalf of follower server B, while saving the original borrow request from follower server B. If follower server C has available allocations, leader server A will decrement the number of allocations in follower server C by the appropriate amount, and increment the number of allocations in follower server B by the same amount. After the distribution table 36 for leader server A is updated, leader server A will send a distribution criteria sync message to follower servers B and C to change their distribution tables 36. However, if follower server C does not have a sufficient number of available allocations, it will decline the borrow request from leader server A. Leader server A will then send a borrow response back to follower server B, indicating that no authorizations could be granted. Because the borrowing process may take a relatively long time, it is possible that while a server is in the process of borrowing allocations, but before any allocations have actually been re-assigned, a new request from another client computer for one or more authorizations may be received. In preferred embodiments of the present invention, the affected server will examine its distribution table, and even though the borrowing threshold is currently exceeded, will grant authorizations to the requesting client computer if there are enough allocations available to satisfy the entire request. However, if there are an insufficient number of available allocations to satisfy the entire request, the affected server will send a denial message back to the requesting client computer. In preferred embodiments of the present invention, because the re-assignment of allocations in the distribution tables 36 of the license servers 14 as a result of a borrow request is not reversed when the re-assignment of allocations is no longer needed, borrowing has the result of dynamically altering the distribution of allocations for each license server 14 in the server pool. Thus, license servers 14 that receive a large number of requests for authorizations may eventually accumulate a large number of allocations as compared to license servers 14 that receive fewer requests. In this way, the current distribution of allocations may, over time, settle into a distribution that is optimized for the utilization of the specific network. Network administrator modification of the distribution of allocations In addition to the re-assignment of allocations as a result of borrowing, the distribution of allocations may also be changed by the network administrator. Although the RLF 24 contains the initial distribution 30, a network administrator may later decide to change the current distribution 40. Preferred embodiments of the present invention provide a utility, triggered by a change distribution criteria message, that enables a leader server to make changes to the current distribution 40 of allocations for the pool of license servers. Using the example three server pool discussed in FIGs. 13-16 for purposes of illustration only, if the network administrator, using a client computer 12, sends a change distribution criteria message including a new current distribution 40 to follower server B, follower server B will pass this message to leader server A along with the new current distribution 40. As this example illustrates, in preferred embodiments all change distribution criteria messages, if not initially sent to the leader server, must be forwarded to the leader server so that the leader server always has a global picture of the current distribution of allocations 40 in the server pool. In addition, follower server B will send a "message forwarded to leader server" message back to client computer 12. Once leader server A receives a change distribution criteria message, leader server A will then change its current distribution record 40 in its distribution table 36 and send a distribution criteria sync message to follower servers B and C. Again, it should be noted that a change distribution criteria message will only change the current distribution 40 of the server pool, not the RLFs 24. An advantage of this utility is that a network administrator can use any license server 14 to make the change. In the case where the network administrator uses a client computer to send a change distribution criteria message directly to the leader server, after the leader server changes the distribution table and a distribution criteria sync message has been sent to the follower servers in the pool, the leader server will send a message back to the client computer indicating that the distribution criteria has changed. In addition to changing the current distribution of allocations in the server pool, in embodiments of the present invention allocations can also be added to the server pool by the network administrator. Through a client computer, for example, the network administrator can run a utility that requests the addition of allocations to an existing license code by adding a "new" license code. The overall hard limit of the existing license code is thereby increased by the hard limit of the new license code. The new license code should accompany a distribution criteria specifying a desired allocation for each server in the pool. If no distribution criteria is specified, the allocation is equally divided among the servers in the pool, with any remainder being placed in the free pool. If the add allocations message is directed to a follower server, the follower server will forward the message to the leader server. Thus, an advantage of this utility is that a network administrator can use any license server to make the change. Once the leader server receives an add allocations message, the leader server will then change its hard limit of allocations record for the proper license code in its distribution table and send a distribution criteria sync message to the follower servers. Once the hard limit of allocations record has been changed in all license servers, the leader server will send a message back to the client computer through the follower server (but only if the add allocations message was initially sent to the follower server) indicating that the hard limit of allocations has been changed. Again, it should be noted that an add allocations message will only change the hard limit of allocations in the server pool, not the RLFs. In embodiments of the present invention a new license code 26 can be added to the server pool by the network administrator. Through a client, the network administrator can run a utility that requests the addition of a new license code 26 to a particular license server. Using the example three server pool discussed in FIGs. 13-16 for purposes of illustration only, if the network administrator, using a client computer 12, sends an add license code message to follower server B, follower server B will pass this message to leader server A along with the new license code 26. As this example illustrates, in preferred embodiments all add license code messages, if not initially sent to the leader server, must be forwarded to the leader server so that the leader server always has a global picture of the license codes 26 in the server pool. Once leader server A receives an add license code message, leader server A will then add the license code 26 to its distribution table 36 and send a distribution criteria sync message to follower servers B and C. Once the license code 26 has been added to the distribution table 36 of all license servers 14, leader server A sends a message back to the client computer 12 through follower server B (only if the add license code message was initially sent to follower server B) indicating that the license code has been added. Again, it should be noted that an add license code message will only add the license code 26 to the distribution tables 36 of license servers 14 in the server pool, not the RLFs 24. In addition, an add allocations message must be separately sent to add allocations to the new license code 26. An advantage of this utility is that a network administrator can use any license server 14 to make the change. Non-redundant license codes It should be noted that the discussion hereinabove has been limited to redundant license codes 26, which are defined herein as license codes 26 having allocations that may be re-assigned to any license server 14 in the server pool. However, in preferred embodiments of the present invention, it is also possible to add non-redundant license codes, which are defined herein as license codes that can be run only on a particular server. Thus, one attribute of a license code 26 is whether it is non-redundant. If an add license code message for a non-redundant license code for follower server B is sent to follower server B, for example, the distribution table 36 of follower server B would be updated, but the change would not be forwarded to leader server A. Thus, leader server A would have no knowledge of the existence of the non-redundant license code. To successfully receive an authorization message to run a program licensed under a non-redundant license code 26 in follower server B, a client computer 12 must request the authorization from follower server B. No other license server 14, including the leader server A, will know of the existence of the non-redundant license code 26. Thus, if a request is made to leader server A or follower server C for the non-redundant license code 26 in follower server B, a denial will be sent back to the client computer 12. No borrow request will be initiated. In addition, if follower server B goes down, the allocations for this non-redundant license code will not be re-assigned to follower server C or leader server A. License balancing - borrowing from down servers Dynamic license balancing after a license server 14 has gone down will be described next according to embodiments of the present invention. Continuing the example of FIG. 16 for purposes of illustration only, assume that a client computer A has requested authorization to use a protected software program and has received an authorization message from leader server A, so that the distribution tables 36 for the three license servers 14 are as illustrated in FIG. 17. Now assume that leader server A goes down. An election process is then triggered, and a new leader server is elected from among the functioning follower servers. New leader server B does not have the global allocation information maintained by the old leader server A. Therefore, upon becoming the new leader server, license server B must now receive this information from the other license servers. As illustrated in FIG. 18, because license server A is now down, within the distribution table 36 for new leader server B, the allocations in use record for license server A (see reference character 42) is set to zero, and the allocations available record (see reference character 38) is set to 38. When new leader server B sends a heartbeat to follower server C, the heartbeat contains information which identifies B as the leader server. Follower server C will send an "ack" in response to the heartbeat from new leader server B, and in the process, will provide information on the allocations in use record and the allocations available record for follower server C. Once this information is received, within the distribution table 36 for new leader server B, the allocations in use record for license server C (see reference character 42) is set to zero, and the allocations available record (see reference character 38) is set to 30. In addition, the record for allocations available for all servers in the pool (see reference character 44) is set to 72. In this manner, new leader server B receives a global picture of the status of all license servers in the server pool. Meanwhile, because of the periodic communication, or pinging, between client computers 12 connected to a particular license server 14 and that particular license server 14, client computer A will soon determine that leader server A went down. Client computer A knows that it has received authorization to run a protected program from leader server A, and therefore knows that it must enter a fail-over mode and look for a new license server 14 from which to receive authorization. Because client computer A receives leader priority list 46 from a license server 14 whenever client computer A receives an authorization, client computer A knows the IP address of every license server 14 in the server pool. Client computer A then sends a heartbeat to the remaining license servers 14 in turn, in the order designated in leader priority list 46, until it finds a server with an available allocation. In preferred embodiments of the present invention, each license server 14 maintains a key table containing a list of all client computers 12 that currently have authorizations issued by that license server 14, even for non-redundant license codes. Thus, when new leader server B receives a heartbeat from client computer A, new leader server B will determine from the key table that it did not previously issue an authorization message for client computer A. Thus, new leader server B will convert the heartbeat to a request, and will issue a new authorization message for client computer A, provided it has an available allocation. In this manner, as client computers 12 formerly connected to old leader server A locate and ping new leader server B, new leader server B will issue authorization messages and adjust its distribution table 36 to include allocations previously managed by old leader server A. The distribution table 36 of new leader server B will then change accordingly. However, if client computer A, in fail-over mode, sends a heartbeat to new leader server B, but new leader server B doesn't have an available allocation, new leader server B will first look for an available allocation in the free pool 48, and then in the available allocation record for old leader server A. However, in alternative embodiments, other sequences may be employed. New leader server B can determine the available allocation record of old leader server A from its own distribution table 36. If an available allocation is located in either of these sources, the available allocation is re-assigned to new leader server B, and the distribution tables 36 of new leader server B and follower server C are updated accordingly. An example of fail-over will now be presented. Continuing the example of FIG. 18 presented herein for purposes of illustration only, assume that client computer A, in fail-over mode, sends a heartbeat to new leader server B. Because new leader server B has four allocations available, new leader server B will issue an authorization to client computer A. The distribution table 36 of new leader server B will then be modified as shown in FIG. 19, where the record for allocations available for all servers in the pool (see reference character 44) is decreased to 71, the allocations in use record for new leader server B (see reference character 42) is increased to 29, and the allocations available record for new leader server B (see reference character 38) is decreased to three. Thereafter, because the borrowing threshold has now been exceeded (29 ÷ 32 = 90.6%), new leader server B will attempt to borrow allocations from other sources. New leader server B therefore first looks for an available allocation in the free pool 48, but no available allocations are in the free pool 48. New leader server then looks for an available allocation in the available allocation record for old leader server A, and finds that 38 allocations are available. An allocation is then reassigned from old leader server A to new leader server B, resulting in the distribution tables 36 within new leader server B and follower server C as illustrated in FIG. 20. It should be noted that in preferred embodiments, new leader server B does not immediately update its distribution table 36 and re-assign all of the allocations from old leader server A to new leader server B. Rather, allocations are re-assigned as needed. This is advantageous, because if old leader server A should come back up, it will receive whatever allocation remained in old leader server A from the distribution table 36 of new leader server B. If new leader server B immediately took all allocations from old leader server A, then old leader server A would receive no allocations when it came back up. In preferred embodiments of the present invention, if no available allocations are found in the free pool 48 or the allocation of old leader server A, new leader server B will attempt to borrow an allocation from follower server C. If follower server C has an available allocation, the distribution tables 36 in follower server C and new leader server B are updated so that the available allocation is re-assigned to new leader server B. An advantage of re-assigning allocations from the old leader server A, if possible, before re-assigning allocations from follower server C, is that because follower server C is still up and working, it can send authorization messages to other client computers 12 that request authorization directly from follower server C, provided follower server C has available allocations. In contrast, the allocations of old leader server A will go unused unless the allocations of old leader server A are re-assigned. It should be noted that in alternative embodiments, borrowing is a utility that can be turned on or off by the network administrator. Commuter licensing The preceding discussion described a client computer 12 requesting and receiving authorization for running a protected software program from a networked license server 14. In the operating environment described above, the client computer 12 must remain connected to the network to continue to run the protected software program. For purposes of distinguishing the above-described system from embodiments of the present invention, the authorizations described in the preceding discussion will be referred to hereinafter as "network" authorizations. Commuter licensing will be described next according to embodiments of the present invention. Commuter licensing departs from the concept of requesting and granting a network authorization between license server 14 and client computer 12, and instead is concerned with requesting and granting a "commuter" authorization between license server 14 and client computer 12. While a network authorization is managed by the issuing license server 14 and the server pool, commuter authorizations, once granted to a particular client computer 12, are managed both by the client computer 12 and also by the issuing license server 14. It should be noted, however, that although embodiments of the present invention described herein include a pool or license servers 14, in alternative embodiments only a single license server 14 is required for issuing commuter authorizations. One practical application of commuter licensing according to embodiments of the present invention is for networks employing laptop or notebook client computers 12 that can readily be disconnected from the network. For example, prior to leaving for a business trip or working at home, a user can request a commuter authorization for one or more protected applications from a client computer 12 connected to the network. Once a commuter authorization is granted, the client computer 12 can be disconnected from the network, and can independently instantiate the protected application one or more times using the commuter authorization. This is in contrast to network authorizations, where a client computer 12 must request and receive a network authorization for each instantiation of the protected application. As described earlier and illustrated now in FIG. 21, a developer of a software program 50 to be protected must link the software program to a corresponding shell program code or library of API functions, referred to hereinafter as a client library 52. The linked software program 50 and client library 52 are then loaded onto a client computer 12. In preferred embodiments of the present invention, a user can request a commuter authorization for a particular protected software program 50 by running a separate utility 54 on a client computer 12 networked to the server pool. In preferred embodiments, this utility 54 enables the user to specify the license server 14 from which the commuter authorization will be requested, and the requested time duration of the commuter authorization. The utility 54 invokes the client library 52 associated with the requested software program 50, which first makes a local check to determine if the client library 52 has already received a commuter authorization. If it has, the utility 54 terminates. If it has not, then the client library 52 sends a request for a commuter authorization to the specified license server 14 in the server pool. The request includes a "fingerprint," information that uniquely identifies the client computer 12 from which the request is made. In alternative embodiments of the present invention, a user can also request a commuter authorization for a particular protected software program 50 by attempting to open the protected software program 50. In preferred embodiments, the client library 52 associated with the requested software program 50 first makes a local check to determine if the client library 52 has already received a commuter authorization. If it has, the protected software program 50 is opened, as will be described in greater detail below. If it has not, then the client library 52 sends a request for a commuter authorization to the specified license server 14 in the server pool, and once a commuter authorization is received, the protected software program 50 is opened. In alternative embodiments, the client library 52 does not make a local check, but immediately sends a request for a commuter authorization to the specified license server 14 in the server pool. In preferred embodiments of the present invention, commuter authorizations and network authorizations can be simultaneously received and managed. Thus, a commuter authorization can be requested and received by a client computer 12 even though the client computer 12 may already have a network authorization for the same protected software program 50. When a license server 14 receives a request for a commuter authorization, the license server 14, under the control of the license management software 22, responds to the request by looking at its distribution table 36 to determine whether it has an available allocation for Application vl.O. Continuing the example of FIG. 14 for purposes of illustration only, assume that a request for a commuter authorization has been made to follower server C. In the example of FIG. 14, follower server C has 30 allocations available, as represented by the available allocations record for each server in the pool (reference character 38) in the distribution table 36 for follower server C. Because it has an available allocation, follower server C sends a commuter authorization message to the client computer 12. As illustrated in FIG. 22, once the commuter authorization message is sent, the distribution table 36 is updated so that the available allocations record 38 for follower server C decreases to 29, and the allocations in use record 42 for follower server C increases to one. In so doing, one of the available allocations for a network authorization has been effectively transformed into a commuter authorization. It should be noted that in preferred embodiments of the present invention, follower server C may receive multiple requests for commuter authorizations from client computers 12, and may grant as many commuter authorizations as there are available allocations. However, if an insufficient number of allocations are available, in preferred embodiments follower server C may then issue a borrow request in an attempt to borrow an available allocation from another license server 14. In alternative embodiments, the network administrator or software developer may limit the number of commuter authorizations that may be issued as a percentage of the hard limit of allocations stored in the hard limit record 28 for a particular protected software program 50. When a commuter authorization is sent to the client computer 12, additional commuter authorization information is also encrypted and sent to the client computer 12. As illustrated in FIG. 21, this commuter authorization information includes fingerprint information 60 which uniquely identifies the client computer 12 authorized to receive the commuter authorization, and a commuter authorization lifetime 56, which in preferred embodiments of the present invention is set to 30 days from the granting of the commuter authorization. In alternative embodiments, however, the commuter authorization lifetime 56 can be set by the system administrator to any value less than the remaining time of the license, as limited by the overall expiration date of the license. The commuter authorization information also includes a check-in value 58, which indicates whether the commuter authorization has been returned to the server pool. The commuter authorization lifetime 56 and the check-in value 58 are stored in persistent memory in both the issuing license server 14 and the client computer 12. Other commuter authorization information may include, but is not limited to, the feature name and version, which identifies the protected software program for which a commuter authorization is granted, and a clock tampering value which, when enabled, allows the client library to detect attempts to tamper with the client computer's clock and invalidate the commuter authorization if tampering is detected. In preferred embodiments of the present invention, the clock tampering value is enabled. As noted above, in preferred embodiments of the present invention the leader server always has a global picture of the distribution of allocations in the whole server pool. Thus, in the present example any changes to the distribution table of follower server C must be communicated to leader server A. Follower server C will therefore communicate the fact that its available allocations count has dropped to 29 to leader server A, and the distribution table of leader server A will be updated accordingly. Thus, as illustrated in FIG. 22, the distribution table 36 of leader server A reflects that the available allocations record 38 for follower server C has dropped to 29, the allocations in use record 42 for follower server C has increased to 1 , and that the record for allocations available for all servers in the pool (see reference character 44) has dropped to 98. Until the commuter authorization is returned or otherwise canceled, the hard limit of available allocations in the server pool is effectively decremented by one. In addition, in alternative embodiments, the commuter authorization lifetime and the check-in value are communicated from follower server C to the other license servers 14 in the server pool and stored in memory so that even if follower server C should go down, the other license servers 14 in the server pool can take over the management of the issued commuter authorization. Referring again to FIG. 21, once the commuter authorization is sent by the license server 14, it is received by the client library 52 that initiated the commuter authorization request. Once received, the client computer 12 can be disconnected from the network, because the commuter authorization information received by the client library 52 allows it to independently perform a function similar to a license server 14. Upon receiving a subsequent or present request to run the protected software program 50, the client library 52 decides if it can authorize the client computer 12 to run the requested program 50 by decoding the commuter authorization information and comparing the fingerprint 60, commuter authorization lifetime 56, check-in value 58, and other information to parameters within the client computer 12. If authorization is permitted, then an instantiation of the protected software program 50 is opened. With a commuter authorization, the client library 52 can open the protected software program 50 multiple times, including multiple simultaneous instantiations. It should be noted that once a commuter authorization has been received by the client library 52, all subsequent requests to open the protected software program 50 will be managed by the client library 52 without resorting to a networked license server 14, even though the client computer 12 may still be connected to the network at that time. The communication, or pinging, that occurs between a client computer 12 that has received a network authorization from a license server 14 has been described hereinabove. In contrast, pinging is disabled when a client computer 12 receives a commuter authorization from a license server 14. Because neither the client computer 12 nor the license server 14 will respond to the lack of pinging when pinging is disabled, communication between the client computer 12 and the server pool can cease for long periods of time. At some point in time within the commuter authorization lifetime, the client computer 12 may be re-connected to the network. In preferred embodiments of the present invention, a user may then return the commuter authorization to the network by running a utility 54 that invokes the client library 52 associated with the requested software program 50 and selecting a check-in function. The client library 52 responds by sending a commuter authorization check-in message to the license server 14 that initially granted the commuter authorization. At that time, the check-in value 58 within both the client library 52 and license server 14 is set to indicate that the commuter authorization has been checked in. Thereafter, the commuter authorization is disabled. Furthermore, within the license server 14, the number of available allocations is incremented by one, and this change communicated to the leader server. If the granting license server is down at the time the client library sends the commuter authorization check-in message, this message will be sent to another license server in the pool, and check-in will be managed by that license server. In alternative embodiments, however, rather than checking in the commuter authorization, the commuter authorization is held by the client library 52 for the full term of the commuter authorization lifetime. It is also possible that the client computer 12 may not be re-connected to the network and may not return the commuter authorization to the issuing license server 14 within the commuter authorization lifetime. As noted above, the commuter authorization lifetime and the check-in value 58 are stored in persistent memory in both the license server 14 and the client computer 12. Thus, if the commuter authorization lifetime ends prior to the return of the commuter authorization, the check-in value 58 within the client library 52 and license server 14 is automatically set to indicate that the commuter authorization has been checked in. Thereafter, the commuter authorization is disabled. Within the license server 14, the number of available allocations is incremented by one, and this change communicated to the leader server. If the granting license server is down and the commuter authorization lifetime ends prior to the return of the commuter authorization, another license server will manage the automatic check-in of the commuter authorization. Situations may occur where a user operating a client computer 12 remote from the network may need to obtain a commuter authorization. In alternative embodiments of the present invention, this can be accomplished by communicating with the network administrator. A user desiring to obtain a commuter authorization for a particular client computer 12 disconnected from the network first invokes a utility which generates fingerprint information 60 for the client computer 12. This fingerprint information 60 is conveyed to the network administrator through non- networked communications such as by telephone, e-mail, or the like. In addition, other information such as the requested software program is communicated to the network administrator. Other information that may also be conveyed includes the license server 14 from which the commuter authorization will be requested, and the requested time duration of the commuter authorization. The network administrator then runs a utility 62 on any of the license servers 14 in the server pool that effectively sends a request for a commuter authorization to the targeted license server 14. If, as described earlier, an available allocation is found, the distribution table 36 is updated so that the available allocations record 38 for the targeted license server is decreased by one, and the allocations in use record 42 is increased by one. The commuter authorization lifetime 56 and the check-in value 58 are stored in persistent memory in the license server 14. In so doing, one of the available allocations for a network authorization has been effectively transformed into a commuter authorization. The network administrator is then provided encrypted commuter authorization information as described above. This encrypted commuter authorization information is conveyed to the user of the remote client computer 12 through non-networked communications such as by telephone, e-mail, or the like. The user then enters this information into the utility, which decodes and provides this information to the client library 52 linked to the requested software program 50. At this point, the commuter authorization has been received, and thereafter both the client computer 12 and the server pool manage the commuter authorization in the usual manner as described above. Therefore, embodiments of the present invention provide an improved system and method for more efficiently managing licenses on a network using a pool of multiple license servers that facilitates communication between multiple license servers so that any license server in the pool may act as a leader server, should the leader server go down. Embodiments of the present invention also allow a client to locate and receive authorization from a new license server, should the old leader server go down. In addition, embodiments of the present invention also allow allocations for multiple vendors to be managed with a single process running on a single license server, and allows a redundant license file containing a new hard limit of allocations and a new initial distribution of allocations to be loaded onto one license server and then copied to other license servers in the server pool. Furthermore, embodiments of the present invention also provide a license management system and method for managing licenses on a network using multiple license servers that allows allocations to be distributed among the license servers and then re-assigned between license servers by updating the distribution tables of the license servers to facilitate a dynamic balancing of allocations among license servers based on actual or expected usage. Embodiments of the present invention also allow allocations to be re-assigned from a nonfunctional (down) license server to a functioning license server by updating the distribution table of the functioning license server to facilitate a dynamic balancing of allocations among license servers based on actual or expected usage. Embodiments of the present invention also provide a system and method for managing licenses on a network using multiple license servers that allows a network administrator to change the initial distribution of allocations, add allocations, or add license codes for protected software. Embodiments of the present invention also allow a particular license server on a particular subnet to be selected by the network administrator to operate as the leader server due to its physical location, speed, or efficiency. Embodiments of the present invention may also allow a client computer to determine which is the best license server from which to seek authorization to run the protected software program, thereby balancing the license management load such that the number of available allocations (for a given protected software program, feature or version) can be adjusted to achieve an optimal distribution for each license server in the pool. Embodiments of the present invention may also allow a client computer to request and receive a commuter authorization from a license server while connected to the network, allowing the client computer to run a protected software program even if the client computer should become disconnected from the network. Conversely, embodiments of the present invention may allow a client computer to request and receive a commuter authorization from a license server while disconnected from the network, allowing the client computer to run a protected software program while disconnected from the network.

Claims: What is claimed is: 1. A system for managing licenses for protected software on a communication network, the system comprising: at least one client computer coupled to the communication network for requesting authorizations to use the protected software; and a pool of license servers coupled to the communication network, each license server programmed for managing a distribution of one or more allocations to use the protected software, the pool of license servers including a current leader server programmed for maintaining a record of allocations for license servers in the pool. 2. A system as recited in claim 1, the pool of license servers further including at least one follower server, each follower server programmed for managing the distribution of allocations for that particular follower server. 3. A system as recited in claim 2, each license server further including memory for storing a status of the allocations for that particular license server; wherein each follower server is programmed for communicating the status of the allocations for that particular follower server to the current leader server. 4. A system as recited in claim 3, wherein each follower server is programmed such that it is capable of becoming a new leader server if the current leader server can no longer manage the distribution of allocations for the license servers. 5. A system as recited in claim 1, wherein the pool of license servers are programmed for communicating with each other and determining when a particular license server can no longer manage a distribution of allocations to use the protected software. 6. A system as recited in claim 1 , wherein the license servers are programmed for preventing the issuance of an authorization to use protected software unless a majority of license servers are functioning and capable of managing a distribution of allocations to use the protected software. 7. A system as recited in claim 5, wherein each client computer that has received an authorization from a particular license server, and the particular license server that sent the authorization to the client computer, are programmed for communicating heartbeats between each other; and wherein each client computer that has received an authorization from a particular license server is programmed for determining whether that particular license server is still capable of managing a distribution of allocations to use the protected software. 8. A system as recited in claim 7, wherein each client computer that has received an authorization from a particular license server but has determined that particular license server is no longer capable of managing a distribution of allocations to use the protected software is programmed for: locating a new leader server; and communicating a heartbeat from the client computer to the new leader server. 9. A system as recited in claim 8, wherein if the new leader server receives a heartbeat from a client computer that has located the new leader server, the new leader server is programmed for: determining if the new leader server had already issued an authorization to the client computer; and converting the heartbeat to a request for an authorization if the new leader server had not already issued an authorization to the client computer. 10. A system as recited in claim 5, each license server further including memory for storing a license file and sequence number; wherein if a particular license server is no longer capable of managing a distribution of allocations to use the protected software, the memory in the particular license server is capable of receiving a new redundant license file and a new sequence number; and wherein if the particular license server is brought back on line and if the new sequence number is greater than any sequence number currently stored in the memory of the other license servers in the pool, the particular license server and the other license servers in the pool are programmed for transferring the new redundant license file to other license servers in the pool. 11. A method for managing licenses for protected software on a communication network, the method comprising: coupling at least one client computer to the communication network for enabling the at least one client computer to issue a request for an authorization to use the protected software over the communication network; coupling a pool of license servers to the communication network for managing a distribution of allocations to use the protected software; and selecting one of the license servers in the pool as a current leader server and maintaining a record of allocations for license servers in the pool with the current leader server. 12. A method as recited in claim 11, further including the steps of: designating other license servers that are not the current leader server as follower servers; and managing the distribution of allocations for each follower server with that particular follower server. 13. A method as recited in claim 12, further including the steps of: storing a status of the allocations for each license server within each license server; and communicating the status of the allocations for each follower server to the current leader server. 14. A method as recited in claim 12, further including the step of determining, by communications between the pool of license servers, when a particular license server can no longer manage a distribution of allocations to use the protected software. 15. A method as recited in claim 11, further including the step of preventing license servers from issuing authorizations to use protected software unless a majority of license servers in the pool are functioning and capable of managing a distribution of allocations to use the protected software. 16. A method as recited in claim 14, further including the steps of: communicating heartbeats between client computers that have received an authorization from a particular license server and that particular license server; and determining, for each client computer that has received an authorization from a particular license server, if that particular license server is still capable of managing a distribution of allocations to use the protected software. 17. A method as recited in claim 16, wherein for each client computer that has received an authorization from a particular license server but has determined that particular license server is no longer capable of managing a distribution of allocations to use the protected software, the method further includes the steps of: locating the new leader server; and communicating a heartbeat from the client computer to the new leader server. 18. A method as recited in claim 17, wherein if the new leader server receives a heartbeat from a client computer that has located the new leader server, the method further includes the steps of: determining if the new leader server had already issued an authorization to the client computer; and converting the heartbeat to a request for an authorization if the new leader server had not already issued an authorization to the client computer. 19. A method as recited in claim 14, further including the steps of: storing a redundant license file and sequence number within each license server; storing a new redundant license file and a new sequence number in a particular license server that is no longer capable of managing a distribution of allocations to use the protected software; restoring functionality to the particular license server that was no longer capable of managing a distribution of allocations to use the protected software; and transferring the new redundant license file to other license servers in the pool if the new sequence number is greater than any sequence number currently stored in any other license server in the pool. 20. A system for balancing a distribution of allocations for protected software over a communication network according to a license policy, the system comprising: at least one client computer coupled to the communication network for requesting authorizations to use the protected software; and a pool of license servers coupled to the communication network, each license server programmed for managing a distribution of allocations to use the protected software; the pool of license servers including a current leader server programmed for updating the distribution of allocations to add at least one additional allocation to a particular license server if that particular license server did not have a sufficient number of allocations. 21. A system as recited in claim 20, each license server further including a borrowing threshold and programmed for determining whether the particular license server did not have a sufficient number of allocations by dividing an allocations-in-use value for that particular license server by a total allocation value for that particular license server and determining if a quotient of the division is greater than the borrowing threshold. 22. A system as recited in claim 21, the current leader server further programmed for updating the distribution of allocations to add at least one additional allocation to a particular license server if that particular license server did not have a sufficient number of allocations at any time during processing of a request for authorization from a client computer. 23. A system as recited in claim 21, the current leader server further including memory for storing the distribution of allocations for all license servers in the pool. 24. A system as recited in claim 21, wherein if the particular license server determines that it does not have a sufficient number of allocations at any time during processing of a request for authorization received from the client computer, the current leader server is further programmed for: looking for a source of available allocations by checking a count of available allocations in a free pool, any down license servers, and the leader server; and decreasing the count of available allocations from the source of available allocations and increasing the count of available allocations for the particular license server if the source of available allocations is found. 25. A system as recited in claim 24, the current leader server further programmed for communicating the updated distribution of allocations in the pool to all functioning license servers in the pool that are not the current leader server through a distribution criteria sync message. 26. A system as recited in claim 23, the current leader server further programmed for storing a new distribution of allocations in response to a change distribution criteria message containing the new distribution of allocations communicated to a license server. 27. A system as recited in claim 26: the license servers that are not the current leader server further programmed for communicating the change distribution criteria message to the current leader server if the license servers that are not the current leader server should receive a change distribution criteria message; and the current leader server further programmed for communicating the new distribution of allocations in the pool to all functioning license servers in the pool that are not the leader server through a distribution criteria sync message. 28. A system as recited in claim 23, the current leader server further programmed for adding allocations to the pool in response to an add allocations message containing a count of allocations to be added to particular protected software communicated to a license server. 29. A system as recited in claim 28: the license servers that are not the current leader server further programmed for communicating the add allocations message to the current leader server if the license servers that are not the current leader server should receive an add allocations message; and the current leader server further programmed for communicating an updated distribution of allocations in the pool to all functioning license servers in the pool that are not the leader server through a distribution criteria sync message. 30. A system as recited in claim 23, the current leader server further programmed for adding a new license code to the pool in response to an add license code message containing a license code to be added communicated to a license server. 31. A system as recited in claim 30: the license servers that are not the current leader server further programmed for communicating the add license code message to the current leader server if the license servers that are not the current leader server should receive an add license code message; and the current leader server further programmed for communicating an updated distribution table containing the stored license codes and corresponding distribution of allocations in the pool to all functioning license servers in the pool that are not the leader server through a distribution criteria sync message. 32. A system as recited in claim 23, the current leader server further programmed for updating the distribution of allocations to add at least one additional allocation to a particular license server if that particular license server did not have a sufficient number of allocations at any time during processing of an update message received from at least one client computer operating in fail-over mode. 33. A system as recited in claim 32, wherein if the particular license server determines that it does not have a sufficient number of allocations at any time during the processing of an update message received from at least one client computer operating in fail-over mode, the current leader server is further programmed for: looking for a source of available allocations by checking a count of available allocations in the leader server, a free pool, and any down license servers; and decreasing the count of available allocations from the source of available allocations and increasing the count of available allocations for the particular license server if the source of available allocations is found. 34. A system as recited in claim 33, wherein if no source of available allocations is found by checking the count of available allocations in the leader server, the free pool, and any down license servers, the current leader server is further programmed for: looking for a source of available allocations by checking a count of available allocations in all functioning license servers not designated as the leader server; and decreasing the count of available allocations from the source of available allocations and increasing the count of available allocations for the particular license server if the source of available allocations is found. 35. A method for balancing a distribution of allocations for protected software over a communication network, the method comprising the steps of: coupling a pool of license servers to the communication network; assigning a distribution of allocations to the pool; coupling at least one client computer to the communication network; and updating the distribution of allocations to add at least one additional allocation to a particular license server if that particular license server did not have a sufficient number of allocations in response to a request for authorization received from a client computer. 36. A method as recited in claim 35, the step of updating the distribution of allocations further including the steps of: assigning a borrowing threshold to each license server; and determining whether the particular license server did not have a sufficient number of allocations by dividing an allocations-in-use value for that particular license server by a total allocations value for that particular license server and determining if a quotient of the division is greater than the borrowing threshold. 37. A method as recited in claim 35, the step of updating the distribution of allocations further including the step of: selecting one of the license servers in the pool as a current leader server for storing the distribution of allocations for all license servers in the pool and for managing a re-assignment of allocations to give at least one additional allocation to a particular license server if that particular license server did not have a sufficient number of allocations at any time during processing of a request for authorization received from the client computer. 38. A method as recited in claim 37, wherein when it is determined that the particular license server did not have a sufficient number of allocations during the processing of a request for authorization received from the client computer, the method further includes the steps of: looking for a source of available authorizations by checking a count of available authorizations in a free pool, any down license servers, and the current leader server; and decreasing the count of available allocations from the source of available allocations and increasing the count of available allocations for the particular license server if the source of available allocations is found. 39. A method as recited in claim 38, further including the step of: communicating the updated distribution of allocations in the pool to all functioning license servers in the pool that are not the current leader server through a distribution criteria sync message. 40. A method as recited in claim 37, further including the step of: updating the distribution of allocations by communicating a change distribution criteria message containing a new distribution of allocations to at least one license server. 41. A method as recited in claim 40, the step of updating the distribution of allocations by communicating a change distribution criteria message further including the steps of: communicating the change distribution criteria message to the current leader server; updating the distribution of allocations in the pool in the current leader server; and communicating the updated distribution of allocations in the pool to all other functioning license servers in the pool that are not the current leader server through a distribution criteria sync message. 42. A method as recited in claim 37, further including the step of: adding allocations to the pool by communicating an add allocations message containing a count of allocations to be added to particular protected software to at least one license server. 43. A method as recited in claim 42, the step of adding allocations to the pool by communicating an add allocations message further including the steps of: communicating the add allocations message to the current leader server; updating the distribution of allocations in the pool in the current leader server; and communicating the updated distribution of allocations in the pool to all other functioning license servers in the pool that are not the current leader server through a distribution criteria sync message. 44. A method as recited in claim 37, further including the step of: adding a new license code for protected software to the pool by communicating an add license code message containing a license code to be added to at least one license server. 45. A method as recited in claim 44, the step of adding a license code for protected software to the pool by communicating an add license code message further including the steps of: communicating the add license code message to the current leader server; updating a distribution table containing the stored license codes and corresponding distribution of allocations in the pool in the current leader server; and communicating the updated distribution table to all other functioning license servers in the pool that are not the current leader server through a distribution criteria sync message. 46. A method as recited in claim 37, further including the steps of: updating the distribution of allocations to add at least one additional allocation to a particular license server if that particular license server did not have a sufficient number of allocations during the processing of an update message received from at least one client computer operating in fail-over mode. 47. A system as recited in claim 1, the pool of license servers programmed for selecting the current leader server as the first license server to be started, and if no license server is started first, for selecting the license server with a highest priority as the current leader server according to a leader priority list. 48. A system as recited in claim 1, the pool of license servers programmed for communicating with each other and determining if the current leader server can no longer manage a distribution of allocations to use the protected software, and selecting the license server with the highest priority according to a leader priority list as a new leader server if it is determined that the current leader server can no longer manage a distribution of allocations to use the protected software. 49. A system as recited in claim 1, the at least one client computer programmed for selecting a license server from which to request authorization to use the protected software. 50. A system as recited in claim 49, the at least one client computer programmed for locating all functioning license servers in the pool, receiving information from those located functioning license servers, and selecting a license server from which to request authorization to use the protected software based on the received information. 51. A system as recited in claim 49, each client computer and each license server programmed for communicating a heartbeat between client computers that have received authorization to use the protected software from a particular license server and that particular license server; and each client computer that has received authorization to use the protected software from a particular license server programmed for determining whether that particular license server is still capable of managing a distribution of allocations to use the protected software; wherein each client computer that has received authorization to use the protected software from a particular license server also receives a leader priority list from that particular license server. 52. A system as recited in claim 51, wherein each client computer that has received authorization to use the protected software from a particular license server but has determined that particular license server is no longer capable of managing a distribution of allocations to use the protected software is programmed for selecting a new license server from which to request authorization to use the protected software. 53. A system as recited in claim 52, wherein each client computer that has received authorization to use the protected software from a particular license server but has determined that particular license server is no longer capable of managing a distribution of allocations to use the protected software is programmed for communicating with functioning license servers in the pool in an order determined from the leader priority list until a new license server from which to request authorization to use the protected software is selected. 54. A method as recited in claim 11, the step of selecting one of the license servers in the pool as the current leader server further including the steps of: selecting the current leader server as the first license server to be started; and if no license server is started first, selecting the license server with a highest priority as the current leader server according to a leader priority list. 55. A method as recited in claim 11, further including the steps of: determining, by communications within the pool of license servers, if the current leader server can no longer manage a distribution of allocations to use the protected software; and selecting the license server with the highest priority according to a leader priority list as a new leader server if it is determined that the current leader server can no longer manage a distribution of allocations to use the protected software. 56. A method as recited in claim 11 , further including the step of selecting, by the at least one client computer, a license server from which to request authorization to use the protected software. 57. A method as recited in claim 56, the step of selecting a license server from which to request authorization to use the protected software further including the steps of: locating all functioning license servers in the pool; receiving information from those located functioning license servers; and selecting a license server from which to request authorization to use the protected software based on the received information. 58. A method as recited in claim 56, further including the steps of: communicating a heartbeat between client computers that have received authorization to use the protected software from a particular license server and that particular license server; and determining, for each client computer that has received authorization to use the protected software from a particular license server, whether that particular license server is still capable of managing a distribution of allocations to use the protected software; and communicating a leader priority list from that particular license server to each client computer that has received authorization to use the protected software from that particular license server. 59. A method as recited in claim 58, wherein for each client computer that has received authorization to use the protected software from a particular license server but has determined that particular license server is no longer capable of managing a distribution of allocations to use the protected software, the method further includes the step of selecting a new license server from which to request authorization to use the protected software. 60. A method as recited in claim 59, wherein for each client computer that has received authorization to use the protected software from a particular license server but has determined that particular license server is no longer capable of managing a distribution of allocations to use the protected software, the method further includes the step of: locating all functioning license servers in the pool; receiving information from those located functioning license servers; and communicating with functioning license servers in the pool in an order determined from the leader priority list until a new license server from which to request authorization to use the protected software is selected. 61. A system for managing licenses for protected software on a communication network, the system comprising: at least one client computer capable of being coupled to the communication network for requesting a commuter authorization to use the protected software and for storing a commuter authorization lifetime representing a time period for which the commuter authorization is valid; and at least one license server coupled to the communication network, each license server programmed for managing a distribution of allocations to use the protected software and at least one license server programmed for granting a commuter authorization in response to a request for a commuter authorization; wherein after a commuter authorization is communicated from a granting license server to a requesting client computer, the requesting client computer may use the protected software while coupled to or decoupled from the communication network until the commuter authorization lifetime expires. 62. A system as recited in claim 61, wherein while the requesting client computer maintains a valid commuter authorization, the requesting client computer may open the protected software multiple times, including simultaneous instantiations of the protected software. 63. A system as recited in claim 61, the at least one license server further programmed for granting a commuter authorization to the requesting client computer and decrementing a count of available allocations only if there is an available allocation in the at least one license server. 64. A system as recited in claim 63, the requesting client computer further including memory for storing commuter authorization information including the commuter authorization lifetime and a check-in value received from the granting license server when the granting license server grants the commuter authorization to the requesting client computer; and the granting license server further including memory for storing commuter authorization information including the commuter authorization lifetime and a check-in value when the granting license server grants the commuter authorization to the requesting client computer. 65. A system as recited in claim 64, the requesting client computer programmed for returning the commuter authorization by setting its check-in value to a returned state and communicating a check-in message to the granting license server; and the granting license server further programmed for setting its check-in value to the returned state and incrementing its count of available allocations upon receipt of the check-in message. 66. A system as recited in claim 65, wherein if the commuter authorization is not returned prior to an expiration of the commuter authorization lifetime, at the expiration of the commuter authorization lifetime: the requesting client computer is further programmed for setting its check-in value to a returned state; and the granting license server is further programmed for setting its check-in value to the returned state and incrementing its count of available allocations. 67. A system as recited in claim 61, the requesting client computer programmed for enabling a user to select the commuter authorization lifetime. 68. A system as recited in claim 61, the requesting client computer programmed for enabling a user to select the license server from which to request a commuter authorization. 69. A system as recited in claim 64, the at least one license server comprising a pool of license servers, and the granting license server further programmed for communicating the commuter authorization lifetime and the check-in value stored in the granting license server to other license servers in the pool when the granting license server grants the commuter authorization to the requesting client computer, so that even if the granting license server should go down, another license server in the pool can act as the granting license server. 70. A system as recited in claim 61, the requesting client computer further programmed for detecting attempts to tamper with its internal clock and invalidating the commuter authorization if tampering is detected. 71. A method for managing licenses for protected software on a communication network, the method comprising the steps of: coupling at least one client computer and at least one license server to the communication network; communicating a request for a commuter authorization to use the protected software from the at least one client computer to the at least one license server over the communication network; granting a commuter authorization to the at least one client computer from the at least one license server and decrementing a count of available allocations within the at least one license server only if there is an available allocation in the at least one license server; and storing a commuter authorization lifetime representing a time period for which the commuter authorization is valid within the at least one client computer; wherein after a commuter authorization is communicated from a granting license server to a requesting client computer, the requesting client computer may use the protected software while coupled to or decoupled from the communication network until the commuter authorization lifetime expires. 72. A method as recited in claim 71, wherein while the requesting client computer maintains a valid commuter authorization, the requesting client computer may open the protected software multiple times, including simultaneous instantiations of the protected software. 73. A method as recited in claim 71 , the step of granting a commuter authorization to the at least one client computer from the at least one license server further including the steps of: communicating the commuter authorization lifetime and a check-in value from the granting license server to the requesting client computer; and storing the commuter authorization lifetime and the check-in value in the requesting client computer and the granting license server. 74. A method as recited in claim 73, wherein when the protected software is no longer needed, the method further includes the steps of: returning the commuter authorization by setting the check-in value stored in the requesting client computer to a returned state and communicating a check-in message to the granting license server; and setting the check-in value stored in the granting license server to the returned state and incrementing the count of available allocations stored in the granting license server when the granting license server receives the check-in message. 75. A method as recited in claim 74, wherein if the commuter authorization is not returned prior to an expiration of the commuter authorization lifetime, at the expiration of the commuter authorization lifetime the method further includes the steps of: setting the check-in value stored in the requesting client computer to a returned state; and setting the check-in value stored in the granting license server to the returned state and incrementing the count of available allocations stored in the granting license server. 76. A method as recited in claim 71, the step of communicating a request for a commuter authorization to use the protected software further including the step of selecting the commuter authorization lifetime. 77. A method as recited in claim 71, the step of communicating a request for a commuter authorization to use the protected software further including the step of selecting the license server from which to request a commuter authorization. 78. A method as recited in claim 73, the at least one license server comprising a pool of license servers, the method further including the steps of: communicating the commuter authorization lifetime and the check-in value stored in the granting license server to other license servers in the pool when the granting license server grants the commuter authorization to the requesting client computer, so that even if the granting license server should go down, another license server in the pool can act as the granting license server. 79. A method as recited in claim 71, further including the step of detecting attempts to tamper with an internal clock of the requesting client computer and invalidating the commuter authorization if tampering is detected.

Inventors: BADIA LOGAN A, CHOPRA SANJAY, DUVVOORI VIKRAM, GUPTA RANA, HANDA SANDEEP, LAL POONAM, RAMAMOORTHY SHANKAR, REDDING MARK E, SHARMA HEMANT, TRIPATHY AJAY, BADIA, LOGAN, A., CHOPRA, SANJAY, DUVVOORI, VIKRAM, GUPTA, RANA, HANDA, SANDEEP, LAL, POONAM, RAMAMOORTHY, SHANKAR, REDDING, MARK, E., SHARMA, HEMANT, TRIPATHY, AJAY
Applicants: RAINBOW TECHNOLOGIES INC, RAINBOW TECHNOLOGIES, INC.
Application year: 2000
Main classification: G06F17
IPC codes: G06F21, G06Q10