Free to read is not the same as free to reuse

Every book in this catalog is free to read. That does not mean every book is free to copy, remix or sell. The license is the part that tells you the difference.

Read, share, remix, sell

A license can grant some rights and withhold others. The most common families in the catalog are Creative Commons, the GNU licenses, Apache, and public domain. Each one answers four practical questions: can you read it, can you share it, can you modify it, and can you use it commercially?

Creative Commons

Creative Commons licenses are built from a few conditions. Attribution (BY) means you must credit the author. ShareAlike (SA) means a modified version must use the same license. NonCommercial (NC) means you cannot use the work for commercial advantage. NoDerivatives (ND) means you cannot distribute a modified version.

A book under CC BY can be used in a course, translated or remixed with attribution. A book under CC BY-NC-ND can be read and shared, but not sold or turned into a modified edition. The short code on each book page is a summary; the full license is linked from the book record.

GNU licenses

The GNU Free Documentation License and the GNU General Public License are designed to keep a work and its derivatives open. They are common in software manuals and older textbooks. If you modify a GFDL book, the result usually has to remain under the same license, and you need to preserve the license notice.

Public domain and permissive licenses

Public-domain books have no copyright restrictions in the relevant jurisdiction. Apache, MIT and BSD licenses are permissive: you can reuse the work, including commercially, as long as you keep the required notices. They are common in technical documentation and open-source books.

What to do before you reuse a book

• Open the license link on the book page and read the actual terms.
• Keep the author’s name and the license notice.
• Check whether the license allows commercial use and modifications.
• Do not assume that “free to read” means “free to republish”.
• When in doubt, contact the author or publisher.

You can browse the catalog by license from the license directory, or read the shorter answers in the FAQ.