The FunRetrospective book is licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported. Basically, that means you are allowed to share the book contents as long as it is properly attributed, but you cannot package or repackage the book contents for sale. So if you buy a copy, you can upload it anywhere for others to view it. Even if you get a copy for free, you are allowed to share it with others.
Not allowing commercial distribution is a way to keep the content available for free. Basically, this license ensures that while the content is free for reading, No one can sell it.
