I never played System Shock myself but I was sure glad to see it on GOG and then it got released on Steam.

This might a little silly but I'm a little bothered by the fact that the Steam version is selling better then the GOG version. (the one with all the extras minus DRM)

But mostly for a reason that I really need to double check on before I say anything more.

Who was it that went through the legal trouble to finally get the rights to sell this game, I was under the impression that it was the GOG staff, but I'm not 100% sure.

-the steam version is not superior to the GOG version in any way (if fact, the issues with the steam release are not yet sorted out completely).
-night dive studios were able to secure the rights to re release the game from the star insurance company. then cooperated with GOG to bring us the first digital release.
-the new patch has been released by an unknown modder/hacker nicknamed "the Raven" on a french forum.
-mods are being developed at systemshock.org.

But the GOG version seems to work fine without mods O.o

It is silly. Steam has a larger user base, end of story. The game is also for sale on gamersgate (also, minus the DRM), where others have indeed purchased.

Despite whoever deserves "credit" for the arrangement, it obviously created no obligation for a monogamous relationship between the game and a single dd service. Enjoy the game. Move on. Life's too short.

Everyone says life's too short I say it's too long.