amok: You pay for your games. You got your games. You can therefore not give them away.
Grargar: You can pay 1 freaking cent for your games. You can choose to pay 1 dollar for an extra Steam key.
This may be of interest to you:
http://support.humblebundle.com/customer/portal/articles/243221-can-i-sell-give-away-my-keys- "Can I sell/give away my keys?
Each purchase is intended for use by one individual. Please read our Terms of Service."
You are duplicating games, that is all to it. The keys are or there so you can have an option of where you want your games. It is not so you can make 1 bundle into 2 or 3 bundles.
Also:
"If I already have a game(s) in the bundle do I have the ability to gift the extra copy in the bundle?
Unfortunately, if you already have a game in the bundle you will not be able to gift the extra games to a friend.
Please consider your bundle a "unit", and not to share copies of the games or Steam keys from it.
If you'd like to give a copy of the games away, we have a system in place that allows you to buy a gift key from www.humblebundle.com so your friends can have access to direct downloads as well as any Steam or other keys we have included."
http://support.humblebundle.com/customer/portal/articles/243192-if-i-already-have-a-game-s-in-the-bundle-do-i-have-the-