All text edits to Wikipedia fall under the Creative Commons Attribution/Share-Alike License (CC BY-SA) with the copyright being retained by the original author; as of August 2009[update], most articles/edits are also dual-licensed under the GFDL. This is a guide for using multiple licensing of one's contributions made to Wikipedia so that they are in the public domain or licensed under alternative licenses in addition to the CC BY-SA license (and GFDL, often). A number of users have chosen to release their contributions under some other license, or even to release their contributions into the public domain.
Dual-licensing under CC BY-SA and GFDL on Wikipedia is required by the Terms of Use for all content that is the sole creation of the contributor. Additional licenses are not required or suggested by Wikipedia, but some users—for a variety of ideological or other reasons—prefer to release their contributions under a wider range of terms.
While all articles in Wikipedia are derivative works based on the first contribution made to the article, each article must be licensed under the CC BY-SA license. (Because the Terms of Use permit importing text authored by others or that you have yourself co-authored with others under solely the CC BY-SA license, it is possible to have articles or sections of articles that are singly licensed. All content that is the sole creation of the contributor must be minimally licensed under CC BY-SA and GFDL.) However, individual contributions are not by themselves derivative works because they do not contain any of the original work, as the copyright still remains with the author. It is within one's rights to license those contributions under any terms one prefers, so long as one does it in addition to also being covered under the CC BY-SA license (and, if you are the sole contributor, GFDL).
Example: Alice and Boris are dual-licensors under the CC BY-SA license and GFDL. Alice also chooses to license her content under Incompatible License A, for instance CC BY-NC, so that it can be incorporated into non-commercial material elsewhere. Candice's content, which she coauthored and previously published elsewhere, only licenses under the CC BY-SA license. Both the CC BY-SA license and GFDL may be used in the following cases:
The initial revision started by Alice or Boris.
Any modifications by Alice or Boris up to, but not including, a modification made by Candice.
Possibly any changes made to the article after Candice by Alice or Boris which do not include the modification made by Candice.
For instance,
Alice creates an article → version available under three licenses (CC BY-SA license, CC BY-NC license, and GFDL).
Boris makes an edit. → version available only under the CC BY-SA and GFDL license, unless Boris's edit was so trivial that copyright would not attach (e.g., fixing a typo)
Alice makes an edit. → version remains available only under the CC BY-SA and GFDL license
Candice imports content. → version available only under the CC BY-SA license, unless Candice's edit was so trivial that copyright would not attach (e.g., fixing a typo)
Boris makes an edit. → version available only under the CC BY-SA license, unless Candice's edit can be separated from the rest of the article (e.g., by removing a paragraph).
One must use some common sense in determining whether Boris's and Candace's edits were trivial or separable enough that Alice's original multiple license survives into Versions 2 and beyond. Where Boris's contributions do upset the multiple license, you may not use his contributions under CC BY-NC unless he releases his contributions under that license. Where Candice's contributions upset license, you may not use her contributions under GFDL or CC BY-NC unless she releases her contributions under those licenses.
To be friendly and able to use the material with other open projects which use an incompatible license other than the GFDL or CC BY-SA license.
To make licensing of material less restrictive. For example, public domain allows totally unrestricted usage for any purpose.
If enough people use a different compatible license, large numbers of articles will be multiple-licensed.
To satisfy a copyright holder's ideological or philosophical opinions, such as a belief that information should be absolutely unrestricted (released into the public domain).
For heavily edited articles, the process of manually sifting through the rat's nest of edits to determine whether an article, or a part of an article, is available outside the CC BY-SA license becomes more error-prone as the number of edits to the article increases. This makes it more likely that an article only available under the CC BY-SA license will be erroneously labeled otherwise, and subsequently used in violation of the license.
One could hypothesize that some ideological fanatics might systematically revert, or eliminate, changes made only under the CC BY-SA license to their favorite articles, so that they remain available under an incompatible license.
Even if those who multiply license their contributions can be identified, the multiple-licensed content may not be useful. For example, only the first, third and fifth words of a given sentence may be multiply licensed, while the rest are CC BY-SA and GFDL-only. Obviously, the multiply-licensed content would be of very little use.
In general, users make their multi-licensing desires known on their user page by way of a banner or some description of their wishes (See User:Jamesday for a complicated example). This is often simply accomplished by adding a pre-made template. See the full selection of licensing templates available.
The scope of a license may vary. For instance, a user may choose to license main namespace changes in one license and talk namespace changes in another. In addition, a user may consider releasing all minor changes into the public domain in order to avoid the problems that trivial changes may have in trying to release an article in a specific license. At the same time, meaningful non-minor changes can be released under a more restrictive license. In the case of the GNU licenses, one can specify certain restrictions, such as specifying a particular version of the license instead of any.
Unless you explicitly specify otherwise, all contributions to Wikipedia are dual-licensed under the CC BY-SA license and the GFDL; therefore, if you elect not to adopt additional licenses, no action is necessary.
Wikipedia is already dual-licensed (or singly-licensed in the case of pages incorporating CC BY-SA content from outside sources) under this as of the June 15, 2009 relicensing.
