What would happen? [Thank you giveaway] [Starts tomorrow though :P]

So I am hoping to get a Humble Bundle key through trade, it contains 3 games (
Alpha Protocol, Company of Heroes, Rome: Total War) but I already own one of them (Company of Heroes).
Before I am going to trade I would like to know if this would be a problem, like me not being able to add it because the product is already owned or somthing.

Thanks in advance!

Thanks for awnsering so quickely!

http://www.steamgifts.com/giveaway/A4TvD/vvvvvv