I have bought a game few days ago, but it seems that I haven't noticed, that (the only available option in shop now) it says "gog key distributed at 09/14/16". So does it mean, I won't be able to play this game on Steam? I'd have to buy an another copy if so? What's the difference between GOG and STEAM versions? Can I somehow 'switch' it? Like, to say "Hey, don't give me a GOG key, give me a Steam key"?