There are only a dozen or so themes that I am aware of and most of those are mainly modified via the CSS as opposed to any real changes to the overall forum structure. You are right about compatibility with older themes but that will always be an issue.

I would be more concerned that the proposed changes would be beyond the comprehension of the average user admin like myself, to adjust to.

As for Gitorious I could care less, I'm just now becoming familiar with Source Forge so that would be a naudefj issue to decide for or against, otherwise I'm not much into "What's in right now" if I was I probably wouldn't be using FUDforum.

One of FUDforums major draws for me is its uniqueness but I see some users who see it as a draw back so dragging it forward might not be such a bad idea.