Originally Posted by commodorejohn
Uhh, no? If someone puts something in the public domain, it's in the public domain. And in the US at least (and I think the UK?) copyright is a "use-it-or-lose-it" affair, so ambiguously copyrighted material can effectively be treated as if in the public domain until it's known that it isn't.
Copyright is valid until either the copyright is transferred or released. In some places one can't simply release a work into the public domain so the only alternatives are transferring to another entity or allowing others to use the code under some kind of licence.
There are people that think copyright _should_ only be valid if using it in some way but that isn't the case. That means the concept of abandonware have no legal basis at all.