Ownership in terms distribution of digital software is a bit funky I guess, but from a consumers point of view, there’s really nothing GOG/game companies can do once you got the installer. You’re effectively owning the bits on your hard drive and there’s nothing they can do to control what you do with those bits. I guess from a lawyers perspective it may be different, but in practice there isn’t much.

I’m not sure what you’re getting at with the licenses though? A game licensed under MIT would be free to share, attribution shouldn’t be much of problem.