I'm interested, but not in direct participation right now.
I am working on group accounting or social-economic relationships in
Django.
I'm currently focused on Pinax (aka Django Hotclub of France):
http://code.google.com/p/django-hotclub/
I intend to add several types of economic relationships to Pinax,
including accounting for loosely organized joint ventures like
software projects. Might work well with your goals.
Pinax intends to create a software developer's edition in a month or
so. Not specifically for designers, but some designers participate in
the project.
You might want to consider building your project on Pinax. Might give
you a lot of social features immediately. (Or like all such
frameworks, might give you more than you want...)
Reply to author if you want to chat more, or you can also find me at
http://pinax.hotcluboffrance.com/