At the moment it seems that unless you get the author's permission first, you can't distribute it. I think it should be the other way around, that is, it can be distributed unless the author explicitly says otherwise either on his site or by a post in a recognised MUGEN forum. This would take care of sites dying, because the stop notice disappears along with the site. If it was in a forum, it needs to be updated (say) every 3 years or it expires. I'd also insist that every distribution of anything contain full credits to the original author(s), together with any limitations or licences as the author requires. That should keep everyone happy.