GoG promoting a code in a video at E3, one of the Internet News outlets started trying other codes, discovered that you get that "free" game announcement without actually checking to see if it worked, started trying other codes again without checking to see if they actually worked and went nuts with it.

edit: We appear to have started discussing it here:

https://www.gog.com/forum/general/free_temporary_keys_giveaway_central_topic/post5249

That makes sense. There's at least one thread around here, some time ago. Year or two? This effect of false positives of the redeem page has been known to a few people in the forums. Not well known though.

overall, I've ended asking support about this situation. If its nothing serious - well, whatever, lets consider it as trolling from them.

But if not - well, atleast, they are aware now, lol

Got official answer from support (picrelated).
Its a bug, but its also sort of feature. Just the weird way, they handle codes.
Also there isnt any hidden giveaway/promotion, at the moment.

I'm a little concerned that this might be a way of hacking up fake redeem codes, as in these are parsable and guessable enough that we could guess codes. I really hope this is not the case.