>What does it say to you that he wouldn't seek legal advice against people selling MAME commercially in violation of the license but he says he has sought it now to use against the rest of the team? Nothing of course; there's no reason to seek advice on something that is as clear as the former and upon which everyone likely agreed. Advise is cheap, if he seeks legal action then you got something.
>there was a large-scale effort .. to contact everyone back to the beginning of time. It may have missed some people. This is the crux of the issue that he raises and it's a matter of being practical versus being totally in the clear legally. No doubt, you guys acted in good faith in the changes you made but unless you have some meaningful way of knowing every contributor ever with absolute certainty then it's simply never going to be iron-clad. So yes, he's being a dick/diva but there is a kernel of truth there; it would be almost impossible at this point to guarantee that every line in MAME is being offered under a license that the original author agreed to. Tack on the evolutionary nature of the project and it becomes even more difficult. You can either worry about it and re-write MAME from scratch (eye roll) or just be practical, do the best you can, and admit it isn't perfect.