Cheap, free or costing a million dollars is irrelevant. It's a working game, period.
Don't want the GOG key?
Fine, give the negative feedback, but don't use the key.
If you use the key and still give a negative feedback you are the scammer.
It's a working game, if a person doesn't want a GOG key then they shouldn't enter the giveaway.
In case the person misses the GOG key warning and enter the giveaway by mistake, they can give negative feedback if they don't want the key.
Entering the giveaway AND redeeming they key means the...
I offered a GOG key and announced it was a GOG key in the giveaway so those who didn't want a GOG key wouldn't enter.
The winner redeemed the key and downvoted the giveaway for not being a steam key.
What is wrong with people?