To answer your first question, I did email them back in May offering help but never received a response. I had a chance to catch up with them at the Federated Social Web Conference, and spoke with a lot of similar projects and we're all interested in a common protocol, so in that sense, we're all "joined forces." However, since their project is Ruby on Rails + MongoDB, and Appleseed is LAMP, beyond the protocol, there's not much collaboration on codebases that can happen.

As for why to donate to Appleseed over Diaspora:

1. Appleseed is a much more mature codebase. We've been in development for a while now, and already have around 80 nodes in the wild.

2. Appleseed has a much more experienced developer at the helm. I've been programming web apps professionally since 1997.

3. We have a much clearer roadmap and protocol specification compared to Diaspora, which has yet to hammer out most any specifics in that arena.

4. Appleseed is much easier to install (about 5 min for anyone who's installed LAMP software before).

5. Appleseed is more ambitious. Diaspora aims to be a social networking app, but Appleseed is a social framework, with an extensible MVC model, meant for building new social components.

6. Diaspora already has $200k. :)