It has always been my hope to have a free/pay-what-you-want print textbook, and based upon the success of this campaign so far, the print version will be free for at least the first print run (the first ~700 copies). I do not plan on charging any money for the PDF/e-book version because I do not believe it is right to charge money for pixels/something requires no resources to make and can be copy+pasted.
However, I also realize that in order to keep the project going for more than 1 print run, so that more than 700 people may own a physical copy of the book, I may have to charge some money for either version. I have been advised that the print version may cost as low as $7 or as high as $20, but I think I'll cross that bridge when I get there.
I really appreciate the generosity of all my backers, and I hope that they share this vision with me, and feel proud that they are advancing the cause of open education to everyone.