F4LL0UT: Don't worry, people ask about that stuff here all the time. It's comprehensible that people are confused when they see a game here that is presumably a Steam exclusive (because any other merchant will only sell keys for the Steam version or something).
MiSs_MaDmAnDy: Thank you. I'm so sorry to have offended anyone. I'll leave it here. Many thanks for all the replies
Not sure if this is what you're looking for, but you can - apparently - add games purchased on gOg to your Steam shelf doohickey client thingamajob. I guess so it can launch right from the client or somesuch. Dunno myself since I don't use that service, but other folks have mentioned that option recently.
Obviously that doesn't do bupkis if gOg don't sell title XYZ, but don't let the lack of a Steam version on gOg necessarily scare you away from purchasing games here since they can be sorta slip-streamed in to Steamworks.