Wikimedia site content is freely licensed. This means anyone can reuse Wikimedia content in any number of ways, for commercial or noncommercial purposes. Under the site's license, you have the freedom to reuse and remix content, provided that the same license is retained for your new creations—a radical departure from traditional notions of copyright. Not only can you become an editor and rewrite Wikipedia articles, but you are also free to use the material elsewhere, as long as you follow some specific and fairly simple guidelines. Reuse is part of the WMF's fundamental aim to distribute knowledge and content as widely as possible. The conditions of reuse come with the license chosen for the Wikimedia sites, which is, in most cases, the GNU Free Documentation License (GFDL), printed at the back of this book. Here we'll briefly discuss reusing Wikipedia content.
The general policy that outlines reuse of Wikipedia content is at [[Wikipedia:Reusing Wikipedia content]], but the legal requirements for reuse come from the text of the GFDL license. The Wikimedia sites can be forked or mirrored (copied) in their entirety, or individual pages can be copied or reprinted. Under the GFDL, direct copying is referred to as verbatim copying, whereas creating new versions of works by changing or adding to Wikipedia content is referred to as making a modified version or producing a derivative work.
If you want to post either a full or partial copy of a Wikipedia article on your own website, reprint the article in a book or magazine, or reprint images, these conditions apply:
New works that use GFDL-licensed content have to be licensed, in turn, under the GFDL: The license cannot be changed. (Because of this clause, the GFDL is often referred to as a viral license.)
You must include a full copy of the GFDL license text with any GFDL-licensed work, to be reproduced in all copies of that work (for websites, this copy of the license should be locally hosted). The license can be found at http://www.gnu.org/copyleft/fdl.html.
You must acknowledge the authorship of the article(s) you reuse; this can mean including either a prominent link to the original article history on Wikipedia or a list of all the authors from the article's history along with crediting text such as, "This page uses material from the Wikipedia article <name of article>."
You must provide access to the transparent copy (in other words, a machine-readable copy) of the article you're using. (The transparent copy for a Wikipedia article can be any of a number of formats available from Wikipedia, including the wiki text, the HTML web pages, the XML feed, and so on.)
You may be able to fulfill the latter two obligations partially by providing a conspicuous direct link to the article hosted on Wikipedia. Moreover, for the purposes of creating derivative works of individual Wikipedia articles, a direct link to the particular Wikipedia article used is generally considered to be in compliance with the GFDL (provided your derivative work is also licensed under the GFDL).
As set out at [[Wikipedia:Copyrights#Definitions and trademarks]], Wikipedia considers each Wikipedia article to be an individual document. Wikipedia does not use invariant sections or cover texts. Fair-use content, such as fair-use images, does not fall under the GFDL license as such, but under the fair-use (or similar) regulations of the country where the media are retrieved; any such images should be credited to their original sources rather than Wikipedia. You can find more information about the copyright policy at [[Wikipedia:Copyrights]]. Content that is also in the public domain, such as older texts or photos from government agencies, can be copied without restriction; but if the text or photo has been modified on Wikipedia, the terms of the GFDL must be followed.