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?
For the record, there was a large-scale effort at the adoption of the current license to contact everyone back to the beginning of time. It may have missed some people, but ultimately we had responses from over 75 contributors and there have been zero requests since then to refuse the new licensing. So while the previous license-by-amendments was handled poorly, there was a real attempt to rectify all issues when the current license was adopted, and that should mean any problems with the amendment licenses no longer apply.
A similar effort is under way now to further clarify ownership and document it in each source file; there will be a formal announcement of this alongside the release of 0.151 as well as other attempts to reach past contributors.