adaliabooks: Gog have an affiliate program?
For promotional purposes, yeah. Certain streamers and YouTubers, as well as some gaming (and other) websites, can get set up with an affiliate tag that they can append to GOG URLs for links. When a purchase is made within a certain amount of time after someone followed that link, the affiliate gets a small bit of money for the referral; and, supposedly, a person registering a new account after following such a link will cause the affiliate to get a bit of money from
all the purchases that that new customer makes for a longer period (I think it was at least a month or two, maybe longer).
Unless you're a major entity, though (an established YouTuber, or a site like RPS or Ars Technica) -- or are on the
GOGcom Stream Team -- I'm guessing it's one of those "don't call us, we'll call you" things. ;)