#1113 DRM: Other DRM
para Steam seguro que no es
"Other DRM" usually means a proprietary DRM solution by the publisher. In this case, I think the most likely candidate is the Kalypso Launcher, but I don't own these games and can't be certain.(Esto sobre el tropico 4)
http://www.gamersgate.com/gametutor?issue=240055
aunque otro dice
Other DRM simply means it's not tied to a client service such as Origin or Steam. Once you download and install it, it's there forever, you own it within the confines of the EULA, unlike games with Steamworks and Origin DRM, which you are simply "renting" and have no ownership of whatsoever. All it means is you can't activate it on any client service, but you can add it to your library in Steam by clicking add game, then add non steam product. You just won't get achievements for it, that's all.
Así que seguramente sea descarga directa de gamers gate...