But some licenses are so restrictive that we can't recommend software published under them. The typical end-user license agreement runs to thousands of words. It's virtually impossible for non-lawyers to know if they are using their software in accordance with licensing terms. Terms of software licenses are often very restrictive.
Many licenses restrict software installation to a specific machine rather than a specific user.
To use a program at work and at home, a user would have to buy separate copies. Linux can be installed on any number of computers, at work and at home, without fear of violating the agreement. This is a boon to businesses that use software on a network, where an entire sub-industry has blossomed to provide license auditing and enforcement software and consulting services. Given the complex character of many license agreements, this can be an administrative headache. The BSA letter does not explain why it was sent to the recipient.