Wow, Humble has really gone downhill after being acquired. Make sure you change the default split, they've made it harder to find! There's an "Adjust Donation" button where you can choose to put more of your money to charity, rather than Humble and the book publisher.
By default, they're only giving the EFF ninety cents of your $18 purchase. That's insulting. And they still have the gall to put up a "leaderboard" for people that paid extra, but probably only 5% of their money went to charity if they didn't think to change the split. What assholes.