Strictly speaking, it depends on whether it's on a list of games given away for free as to whether making a giveaway for it is impossible. If a game is given away in limited numbers (such as here), it's not the same as being offered for free in large numbers, and it won't be put on the list.

The game also had a closed beta late last year. It's possible the commenter is referring to a beta key. Beta's can't legitimately be used for a giveaway, but what happens on Steam chat isn't overseen by Steamgift rules (not sure if there's about soliciting trades in someone else's giveaway).