Originally Posted by MT Alex
BlackOmega posted in the other thread that these aren't giftable?
If you already have games listed and redeem the code in Steam, you will not get additional keys or copies to send to other ppl on Steam. This is pretty much how Steam always handles duplicates- except in very rare promotional cases (Left 4 Dead 2 bundles allowed you to gift the extra copy of L4D1 and Portal 2 allowed you to gift Portal 1 (I believe)- for example).
The codes you receive after payment @ HumbleBundle.com can be given to anyone, just like with any other Humble Bundle.