Do you mean a twitter client (like twhirl or twiiferic) or a twitter clone that is open source?
I would love to build a open source twitter clone. But then again it's about the people and API apps, etc and I can't think of a way to duplicate these. Oh... you should also check out http://bitlog.org/ which is a twitter clone by John Resig (which he hopes to one day open source). Anyway, I'm all for writing a Twitter clone that is meant to serve users and users only.
I agree with you on "Either way, I don’t see what there is to be gained by picking one social tool over the others." In the end, after any social media becomes big, it will eventually become like Digg. So, the only way to create a better social media site is to have something that is completely open, transparent and owned by the community.
