If you buy a game on GOG, there's an option to share it on social networks.

The "Google+" option should be removed though. It's not available anymore (at least not for general public).

It's on more than just the purchase completion pages.

GOG's not the only one to still have it lingering around either. I have to guess that it'll be removed eventually (by everyone that's left it up) but it must be extremely low priority to get it done.

Besides, I can't imagine hardly anyone bothering to click it when Google+ was still a thing and the numbers now can't possibly dip below 0 so it's just an "ignore it, it'll go away" situation at this point.