QuakeForge is always in constant development. Our development version has the latest features, but changes rapidly as bugs are fixed and features are added. Stable versions do not change significantly once released, though we sometimes make revisions of the stable branch to fix known bugs.
Newtree is the beginning of a new way of thinking about the source tree. The code in this tree is based specifically on Id Software's QuakeWorld 2.40 source code. There is no support for NetQuake/UQuake in this tree in order to keep it as bug-free as possible. Development is fast and furious, here's where the action is!
QuakeForge: NUQ (pronounced "Nuke") is, basically, the Classic Quake version of Newtree. NUQ is based on the WinQuake engine, but with lots of enhancements from the merged tree and Newtree. Being the reverse Newtree, there is no support for QuakeWorld multiplayer protocols.
Since current work is based on Newtree and NUQ, the merged tree snapshots are no longer being made. You can still get it directly out of CVS, however.
QuakeForge 0.1 is our initial offering to the public. It's not really for end-users, but served as a proof of concept that the Quake and QuakeWorld trees are more closely related than initial look would indicate.