[Apache] Lots of help from a large community of users, but with no strong central push from salaried developers, releases tend to be infrequent and insignificant in terms of new capabilities. (This is one of the dirty secrets of the open-source world; it is easy to get new modules contributed but hard to get everyone coordinated enough to make major changes in the core.) [AOLserver] 
New server software and ideas from one of the world's highest-volume Web publishers, plus a bit of help from the community of users. Releases come in response to major new needs at AOL.