if you've included DOOM in that list, it's not abandonware.
-removed-"It's not piracy if the 20 year copyrights are expired!"
Copyrights last the life of the author and 70 years.
from what i understand this law is relatively recent, like my dad's generation recent.
It came about in 1978, so pretty much everything on the Atari 2600 and beyond is still copyrighted.
open ttd