"Flat World Knowledge is a textbook publisher, focusing on (mostly entry-level) college textbooks. From its beginning until the end of 2012, Flat World Knowledge licensed all of its books under a Creative Commons by-nc-sa 3.0 license, allowing anyone who so desired to copy them, give them away, or modify them, as long as they acknowledged the authors, released the copies under the same license, and didn't do so for commercial gain."