The Citizendium is free to read here and reproduce elsewhere, provided that you meet just a few easy conditions provided by our license. More briefly, CZ is free, with some small caveats! When you contribute to the Citizendium, you're agreeing to let anyone reuse your contribution elsewhere, for a very wide variety of purposes. We think this benefits the world.
All original articles are available under the Creative Commons CC-by-sa 3.0 license. The Citizendium Foundation reserves the right to upgrade the license version number (not the license) on behalf of contributors. Articles that originated in part from Wikipedia are available under the CZ:GNU Free Documentation License 1.2 or whatever license number(s) or other licenses the Wikimedia Foundation permits.
The Citizendium adopts CC-by-sa 3.0 Unported (original source) as the license for our own original collaborative content. This means (among other things) that, if you start a new article for the Citizendium, "from scratch," then when you press the "Save page" button, you agree irrevocably to license your text using CC-by-sa. We say "our own original" to exclude articles that originated elsewhere (usually Wikipedia), and we say "collaborative content" to exclude such possible non-collaborative features as "Signed Articles."
The Citizendium will continue to use the GFDL (original source) for articles that originated with Wikipedia, at least until such time as Wikipedia has credibly announced that we may relicense such material under CC-by-sa. At that time the Citizendium Foundation will announce that all articles are relicensed under CC-by-sa.
We use a variety of other licenses, in addition, for our non-text media.
Reproducing Citizendium content elsewhere
As to articles that originated with the Citizendium, you are free both to reproduce and to further develop them as long as you link from your copy back to the original Citizendium article, and do so reasonably prominently (no hidden or tiny print). You must also link to a copy of the CC-by-sa (or GFDL) license.
As to Citizendium articles that originated on Wikipedia, we expect Wikipedians to credit and link to the relevant Citizendium article if they wish to use content that the Citizendium contributed to those articles. If you are a third party site, you must credit both Wikipedia and the Citizendium for these articles, and note that the applicable license is (again, for now) GFDL, not CC-by-sa.
As to images and other media, and signed articles, consult the license information for the media or article. There are many free images (public domain, CC and GFDL) in our media collection, of course, but you may not simply host them all with no attention to licensing matters. We apologize for the inconvenience to our reusers, but this is a decision we have made, so that our own media offerings are as fine as possible.
In general, you can most easily and safely reproduce the text of our collaborative encyclopedia articles, and all other text content that we have developed collaboratively (which is all of the text of our collaborative encyclopedia articles, and the vast majority of the text on subpages).
For instructions about how to reuse our content, with special attention to reuse by Wikipedia, please see Reusing Citizendium Content.
Implications for using Wikipedia articles in the Citizendium
Bear in mind that someone who is the only author of some text that is used by Wikipedia in effect relicenses his or her contributions under CC-by-sa, if he or she does not check the "Content is from Wikipedia?" checkbox. Many Citizens have already uploaded their solely-created content without giving credit to Wikipedia. But note that if, in "your" Wikipedia article, even a very small edit was made by another Wikipedian, however, we must give Wikipedia credit and use the GFDL for that article. Unless you produce a version of the article that is entirely your own work, you personally lack the standing to remove the Wikipedia credit and license.
Bear also in mind that we allow people to upload images and some other media to the Citizendium under any legal arrangement that permits unpaid access by our readers. The most restrictive such arrangement is that you simply give us a permanent right to use your media on the website and any future Foundation publishing projects (which will, of course, be nonprofit); but otherwise you retain all copyrights.
Of course, all of our content can be found and downloaded using any standard Web browser.
For computer programmers who wish to download our content all at once, we have prepared a "database dump" that we will be updating regularly, consistent with usual practice. Non-technical people will find these files useless.
An expectation of support from large reusers
A significant portion of the Citizendium's contributors are not comfortable with the idea that their work might be "exploited" by "profiteers," with no compensation being given to themselves individually or even to the Citizendium Foundation.
Therefore, the Citizendium Foundation advances the proposition that those who succeed in making significant profits from reuse of the Citizendium's content are morally--not legally--obligated to share some nontrivial portion of those profits with the project. In other words, while we ask that you share any profits with the project, this remains a well-grounded request and not a requirement.
Of course, we understand that most commercial concerns "know what side their bread is buttered on," and would naturally voluntarily share some of their profits with a charitable enterprise that makes those profits possible, without our asking them to do so.
An option to legally represent
We may in the future take up the issue whether the Citizendium Foundation should represent the Citizens who have contributed content, in case we would like to sue for violation of our license. Such a lawsuit could be a class action suit. For now, we are setting this issue aside.
In the meantime, please be aware that both the GFDL and CC-by-sa automatically terminate the reuser's rights if they fail to abide by the license terms, including about how attribution is done. Please, let's not so much as even have to think about ever having to go there. Honor the licenses and attribute the material as stipulated.
A 22,000-word essay was produced in December 2007 by Larry Sanger, with the help of many others, that explains our choice of license: "An explanation of the Citizendium license."