KolyaKorruptis: You can download the game and it runs out of the box. If you have money to spend there are more worthy causes than 20 year old computer games:
http://www.greecedebtfree.org/donate Same thing is true for most games, either new or old. That's why I asked if I can legally buy it, not if I can find it somewhere.
If you cannot see that difference, then there's no use discussing it further. Why should GOG try to obtain any other game, since they can be downloaded and played out of the box.
And as for the link, you could find a better cause, since the GDF works under the assumption that it can either collect €4.5 billion to buy all the bonds at once, or that after it starts deleting the first bonds (€1 billion worth of them?), the bonds value will increase, so the projected €4.5 billion will be closer to €450 billion.
So if that's your "more worthy" cause, then I do believe that the enjoyment of a game (or two hours of voluntary work) are more worthy than donating to GDF.