Abandonware is only abandonware if it has been explicitly released by the owner
It could also lose its copyright... though any game currently that is abandonware that way is ungawdly old.
... have
any of them actually had that happen, yet? Last I remember, copyright's lifetime+70, and I'm fairly sure there
weren't video games that far back. We've still got a bit before that becomes a possibility.
That said, legit abandonware par excellence:
Warzone 2100. Released free to the public back in '04, further developed by the community since. Once of the best RTS games of the 90s and, honestly, early '00s. Very nice piece of work.
Though @ Ultimuh: Again, even though a lot of times it's let slide and generally no one really cares about it (So you've got stuff like HotU that has a lot of games up that, frankly, are illegal to redistribute, but no one stops 'em), the legal aspect is pretty cut and dry. If it's under copyright, it's under copyright. Age or lack of being sold doesn't remove copyright. Almost always, if it's not been specifically released to the public by the owner(s) -- and
most "abandonware" hasn't been -- it's not actually
legal to redistribute. Now, me, I don't really care (and I don't think boss Toad really
minds it on a personal level, per se, from what I remember), but the forum ToS is what it is, and should be respected insofar as that goes.