> Having a MUGEN free software game would be awesome.
That depends. M.U.G.E.N. was actually one of the games I suspect may belong on this list, but I haven't been able to find any definitive answers. All of the information I was able to find was on how to use particular (proprietary) IDEs to make M.U.G.E.N. characters, which isn't particularly helpful.
If my suspicion is correct and some parts of the characters are some kind of script, then a libre M.U.G.E.N. implementation would be mostly useless on its own.
> Does anybody knows of any free software 2D fighting game or any MUGEN clone being developed right now?
I'm not aware of any Street Fighter type fighting games, if that's specifically what you mean. However, there are other kinds of games that I would classify as "fighting games". The Ur-Quan Masters, for example, includes "Super Melee", which is one-on-one ship combat. (The Ur-Quan Masters is not libre culture, but all software is libre; the proprietary data doesn't include scripts of any kind.) But depending on what you like, that might not be helpful; maybe you don't like that combat in that game primarily uses bullets, for example.
One other game of interest is Slappa. It's not really a fighting game, but does have somewhat of a Street Fighter feel to it.
I do have a goal of making a good Street Fighter II clone at some point in the future, if no one else does it first. The same goes for a Super Smash Bros clone. I don't know when exactly I'll do these, though.
