phandom: Can I gift the second copy or will I lose the game from GOG too?
PaterAlf: You won't loose your GOG copy, but you're not supposed to give away the Steam key when you redeemed the game on GOG. As far as I understand it, you got one license for the game when you bought the bundle. They give you the choice where to redeem the game (or even to reddem it on both services
for yourself), but you shouldn't double the license by keeping one key for yourself and giving away the second one. It's not fair to the developers in my eyes.
I believe Humble sometimes does include multiple licenses of games in bundles. For example, according to the
Gifting Steam Keys support page: "The gifting process will only give the recipient the Steam key. If there is a soundtrack or DRM Free copy of the game in the bundle, you will still retain ownership of it and it will stay on your download page." I don't see anything mentioned about keys for multiple platforms, probably because it still isn't very common, but if they are both listed as separate keys and the gifting function isn't deactivated after redeeming one, I would assume that they're two licenses at least from a legal standpoint (whether it's fair to the developers or not is another question).