A ticket was filed this weekend for FESCo, the engineering committee for the Fedora project, to clarify their position on forks like Muffin, Mate, and Cinnamon (i.e. the GNOME desktop forks).
From the one that opened the ticket, "I have serious concerns about letting forks like these enter Fedora - not to mention the zombie called Mate. Therefor I think we should clarify our position on forks in general and these ones in particular. Would be nice to get an upstream statement from one of you guys."
Bringing the MATE desktop into Fedora was brought up last December. MATE, which comes down to maintaining/preserving the GNOME2 packages, hasn't seen much traction or advancement as quickly responded, "I think packaging forks is fine if you want to scratch your itch, but you are likely to waste a lot of effort and I don't really see how it helps Fedora. If in doubt, I'd rather see you contribute upstream to an existing project such as Xfce, KDE or GNOME. It is a lot of fun !"
Yesterday at the FESCo meeting they determined, "At the 2012-02-27 meeting we agreed to forks are allowed provided they do not conflict or interfere with other packages. FPC may add additional guidelines to forks as they see fit."
This would mean Ubuntu's Unity desktop, for example, would have a hard time making it into Fedora since it still conflicts with some upstream GNOME libraries at present. But for forks where packages don't collide, FESCo apparently is willing to let them in at this point.