On the surface, this is different from YP only in the server application and protocol used to shuffle the data back and forth. The major difference, however, is in scope. YP was a great idea for it's time, and Sun perhaps did a their job a little too well. YP was such a great idea that nobody bothered to extend it for quite some time, and it really needed to be extended. The format of the information YP stores is so closely tied to the format of various Unix configuration databases that YP was only useful for storing Unix configurations.
System configuration is a topic that has raged back and forth in FreeBSD since the early days.
A few small and useful programs have issued forth from the discussions, but none have been widely adopted. A good project for BSD, one what would require an architect or two, and several willing programmers of fair to middling talent, could modify the current login system to support replaceable authentication modules, so users could select not just what format they want their passwords stored in, but where they want them stored. This is already done in a limited way for NIS, we need to extend it to a general capability. Ideally, the system administrator would select which configuration method they want to use at sysinstall time, and could then change it in the future by rerunning sysinstall, or by installing a package and modifying a configuration file somewhere. The two current no-brainers for format would be Radius, because it is already widely used by ISPs and contains most of the information needed about user accounts already, and LDAP because it truly is the directory of the future.