I'm not too sure about all the details, but from what I get:
-If a campaign is successful, the book will be released under a CC license and anyone will be able to get it for free. I think the license is mainly for the non-commercial, non-derivative rights. (
some info on their FAQ here)
They also say that this doesn't mean that the rights holder can't make money for the book, selling other print or ebook editions. I guess it just means that there will also be an unglued edition out there. (there's more about this
here)