I've seen a dozen community projects fail miserably or never get off the ground at all. It's a cool idea but never pans out.
The best you can do is get a very small and competent dev team with a solid idea and workflow utilizing contributions from the community - but good luck getting so many people from various backgrounds to work in the same art style and so on.
On that note, I'm sorry, but C2 is pretty bad when it comes to collaboration of any sort. It works with SVN, but it wasn't necessarily designed from the beginning to do so. Things like default instances and external resources can cause all kinds of trouble.