Plan 9 Newsgroup is Revived (comp.os.plan9)
Plan 9 is a Unix-like operating system first developed by Bell Labs.
https://comp.os.plan9.narkive.com/SnexHy94/we-re-alive-again
"comp.os.plan9 is a moderated newsgroup for discussion of the Plan 9 operating system and related systems. It's a forum to ask questions and share information about installing, administering, using, and developing the system. Discussion of the original Plan 9 from Bell Labs as well as all forks, derivitives, or otherwise related systems are on topic. "
http://9srv.net/comp.os.plan9/index.html
Where is the source code used for the newer plan 9 development? (the foundation said they are participating in google summer of code).
Days late, but the sources can be found in a few different places depending on what you're looking for.
The "official" Plan 9 (a.k.a. 4th Edition from Bell Labs) as controlled by the Foundation can be found here.
After that there are a few different "development" branches, so to speak. There's 9legacy, which is basically Plan 9 with some patches for modern hardware, and then there's 9front, which is where much of the real development of Plan 9 actually occurs. Others also exist in varying states of development/decay — 9atom, harvey, and r9, mainly.
9front is where most of the action is these days, but it's not "official" in that it isn't directly controlled by the foundation. However, at least one member of the foundation (Ori Bernstein) is a primary contributor and developer.
One of the newsgroup moderators probably knows the answer.