I found a gog key for Earth 2160 on a Bundle and i think (almost sure) it's unused, anyone wants to give it a try?
You can try to redeem it without using it. GOG tells you what is the key for, if it expires and will ask you to confirm the operation.
Oh, thanks for the info, so, the good news is that it wasn't used, the bad news is that i got this message "Code expired on: June 30, 2014".
Nothing to see here, move along...