It seems like several people have been having problems playing the game due to it demanding a CD key before it lets you play. Has this been fixed, or am I going to have to ask GOG support for a key before I can play the game?

Never mind, my mistake. I just noticed the small print that mentions that you only need the CD key is you want to play multiplayer, which is fortunately completely uninteresting to me.

If you mean Earth 2160 then you can do NOTHING AT ALL without this key! Well, my copy won't anyway!

GOG need to pull their fingers out from their arses on this one!

Sorry about the delay, I wasn't notified about you quoting me.

Yes, I mean Earth 2160. It seems to have some issues with DRM, but looking at the forums it seemed to have been solved. It is a shame that it turns out to still be a problem.

I can't remember getting a CD-key with the download. Where do I find it?

GOG don't give you a key at all with Earth 2160, they do with every other game, so why this one is an exception is a mystery. GOG seem very unable to fix this too! You will have to contact support to request one! :/

GOGmix: GOG Games With Serial Numbers. Support link and choose multiplayer key request.

Never tried multiplayer myself, but singleplayer, game installed to K:\, worked without the extra CD-key.