As always, you can choose which portion of your donations go to the developers, to the charities (Child's Play and the Red Cross!) and to the Humble Indie Bundle platform itself. We think we speak for everyone when we say that this is an insane value that you'd be insane to pass up, you insane person.
[Update: Tim Ambrogi from Philly-based Jamestown-dev Final Form Games told us, "It's been our goal since launch to reach as many gamers as possible, so a Mac and Linux port were always our plan if we could afford the resources to develop them. Humble Bundle presented us with a cost/benefit proposition that made creating them now a low-risk decision." That's your money hard at work, people!]