Wikibooks

Wikibooks (previously called "Wikimedia Free Textbook Project" and "Wikimedia-Textbooks") is a wiki-based Wikimedia project hosted by the Wikimedia Foundation for the creation of free content digital textbooks and annotated texts that anyone can edit.
Initially, the project was created solely in English in July 2003; a later expansion to include additional languages was started in July 2004. As of , there are Wikibooks sites active for languages comprising a total of articles and recently active editors.
History.
The wikibooks.org domain was registered on . It was launched to host and build free textbooks on subjects such as organic chemistry and physics. Two major sub-projects, Wikijunior and Wikiversity, were created within Wikibooks before its official policy was later changed so that future incubator-type projects are started according to the Wikimedia Foundation's new project policy.
In August 2006, Wikiversity became an independent Wikimedia Foundation project.
Since 2008, Wikibooks is included in BASE.
In June 2016, Compete.com estimated that Wikibooks had 1,478,812 unique visitors.
Wikijunior.
Wikijunior is a subproject of Wikibooks that specializes in books for children. The project consists of both a magazine and a website, and is currently being developed in English, Danish, Finnish, French, German, Italian, Japanese, Spanish, and Arabic. It is funded by a grant from the Beck Foundation.
Book content.
While some books are original, others began as text copied over from other sources of free content textbooks found on the Internet. All of the site's content is released under a Creative Commons Attribution-Share Alike license (or a compatible license). This means that, as with its sister project, Wikipedia, contributions remain copyrighted to their creators, while the licensing ensures that it can be freely distributed and reused subject to certain conditions.
Wikibooks differs from Wikisource in that Wikisource collects exact copies and original translations of existing free content works, such as the original text of Shakespearean plays, while Wikibooks is dedicated either to original works, significantly altered versions of existing works, or annotations to original works.
The project is working towards completion of textbooks on numerous subjects, which founders hope will be followed by mainstream adoption and use of textbooks developed and housed there.
Multi-lingual.
As of , there are Wikibooks sites for languages of which are active and are closed. The active sites have articles and the closed sites have articles. There are registered users of which are recently active. 
The top ten Wikibooks language projects by mainspace article count:
For a complete list with totals, see Wikimedia Statistics.