The Gnutella Developer Forum
From iA wiki
A discussion group hosted at Yahoo focused on the development of the Gnutella protocol. The file area contains several protocol specifications and RFCs, covering topics such as ultra-peers and web caches.
The official site is at groups.yahoo.com/group/the_gdf.
Competing factions may be found at Gnutella Forums Development Forum along with many Gnutella users.