The guys added the games from the first Humble to the offer, the games are all remedable on Steam for new purchasers, the Humble Indie Bundle #1 is only unlocked if you pay more than the current average (which is 7.39 $ the moment i am writing). If you’d like to pay under the average and increase your payment later on your download page, that will work too.
Steam keys for the Humble Bundle #1 are a little glitchy: they don’t unlock Samorost 2 or the Mac versions of Gish and Aquaria. A fix is being worked, no guarantees through. Additionally, only 150,000 keys are available. First come first serve basis, maybe more keys will be added but no guarantee. Also, no promises about activating HIB #1 games on Desura at the moment.
The offer is limited (will end in some days).