You can join it here:
http://lists.bbpress.org/mailman/listinfo/bbdev
I have joined; I want to find out more about these "plugins" of which they speak. If we're going to make changes, doing it in a modular way will definitely be better than crudely hacking the code. :)
Apparently bbPress is designed with the addition of plugins in mind. I have yet to find anything like an index of them.