The full book is released under the Creative Commons BY-NC-SA 3.0 license. If you are unfamiliar with Creative Commons licenses there are many books and online sources which explain their history and purpose.
As an internationally collaborative book writing initiative, the book was made better by building on top of each others work. Traditionally a book would be released using an ‘all rights reserved’ style license. But why stop building on each others hard work once the book is finished? What about allowing the book to be a seed that enables the creation and development of other projects/initiatives/works?
We believe that by opening up the book to an appropriate Creative Commons license we as a species stand to benefit the most from our hard work in creating the book. Just as the problem of global warming is one which we have to collaborate and harmonise our efforts to solve, the book was also completed by collaborating and harmonising and we want this to continue into future projects/initiatives/works.