As far as I understand, under the GPL the only action that is really mandatory is sending the source code after a private request from someone that obtained a copy in binary form. There is no need to put the code in some public website or something. I think that the question that tackles with this problem is this one: http://www.gnu.org/licenses/gpl-faq.html#WhatDoesWrittenOfferValid
In this way, Exophase has the right to ask for the Mame4all code in private, and after that he can publish the code in his website.
But the fact is that in the free and open source communities, the normal behavior is that the authors publish the source code in a public location, and in this way there is no need of any private request. I support this approach, and then I kindly ask to the Mame4all authors to put their code in a public website, even if I think that they are not really committed to this.