RetroJaro: If you care to, can you post where it says not to give away your spare keys? I skimmed over the terms of service with searching a few keywords and didn't see anything about it.
My intention with giving away my spare key is not to breach rules, but to give the game to someone who can't, or won't, purchase the humble bundle and wants to play this.
I guess the next question is, should I bother keeping this open?
Even when they were having all in one keys, I remember getting extra copies of games in my inventory a few times. I even gave away a few on here.
Edit 2 - and if you ask for my opinion, I would say that the honourable thing would be to close the giveaway.