Foxhack: So is it okay if I give away extra keys for games I already got in another bundle?
nmillar: The organisers of the Indie Royale Bundles have stated that you can "do what you like" with the extra keys you have. With these bundles, you are given a separate key for each game, so as long as you haven't redeemed any of the keys associated with a particular game, you are welcome to give it away.
On the flip side, the Humble Bundles have one key for the entire bundle. Redeeming a Steam key, then giving away the Desura key for the same bundle is against the rules. If you want to give anything away here, you should be purchasing an additional gift copy of the bundle.
I wouldn't give away Desura keys (or full-set keys) since they're for an entire set of games.
Single game keys for stuff I already owned and paid for separately, though, I think that's fair.