Pheace: Quite a few games have 1 key - 1 profile - 1 user though, and you really only get one key from GOG, even if you ask.
Correct me if I'm wrong.
Most games come with a generic key (or without one) and either don't care about it for the single player or they use a modified executable. For the multiplayer part, some games identify the game session through the cd-key used, thus the key needs to be unique, other games identify the game session through other means (UT for example). In the second case, a unique cd-key isn't needed to play (I know of that because we did have 16man matches of UT back in 2k with a single installation). There are also a few more games that require an account to log in and play, with said account needing to have a unique cd-key again, though that should be patchable (didn't NWN have that thing as well? Some servers require it, some don't).
So, what does the 1 key - 1 profile - 1 user have to do with the engine limitation I mentioned above?