Commons:Choosing a license

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This page is a guide to people who are contributing their own work, and want advice about free licenses and the "best" one to choose to apply to their work.

If you don't want to read this and just want to know which license the Commons community recommends, choose one of the following:

• {{CC BY-SA 4.0}} (some rights reserved – attribution and sharing alike required)
• {{CC BY 4.0}} (some rights reserved – attribution required)
• {{CC0}} (no rights reserved – public domain or waiver if the PD release is invalidated)

However it's better if you read the rest of this page, to understand what you're agreeing to!

Ideology and philosophy

Copyright is a form of intellectual property law that gives the creator of an intellectual work the right to control how that work may be used. However, the creator may choose to give up some of the control.

The creator holds the copyright. Under traditional ("proprietary") licensing, the creator (say, a novelist) sells a specific license to a specific person (say, a book publisher, or a movie producer). When an author puts a work under a public license, however, they allow anyone to use their work, under certain conditions.

People who are anti-copyright believe that the current copyright system and/or any copyright system is inappropriate and should be severely curtailed and/or abolished altogether. If you are anti-copyright, you probably will want to release your work under a public license which waives as many of the author's copy rights as possible (releasing into the public domain is not legal in many countries, but you can use CC-0). See the "Public domain and approximations" section.

Copyleft is the idea of using the copyright system to remove the common restrictions used in copyright, and prevent others from re-imposing them. People who advocate for copyleft may or may not be anti-copyright. If you believe in copyleft, you will probably want to use one of the free licenses detailed in the "Copyleft / Sharelike" section.

A creator may issue a work under multiple licenses, public or proprietary.

The software model

Android has changed licenses, which would not have been possible with a copyleft license

The model of software programs is well-known, and has been successful in a range of applications, from entire operating systems (Linux) to the software that is used to run Wikipedia and its sister projects (both use copyleft GNU General Public Licenses; see below). The key features of this software are:

• right to view the source code (open source)
• right to modify the source code (right-to-adapt)
• requirement that any modified versions of the software are released under the same license (copyleft/sharealike)

It is possible to mix-and-match these features. However, works under different copyleft licenses can usually only be combined if the license explicitly allows it.

Some open-source software licenses omit the sharealike condition. These are called "permissive licenses"; they mean that re-licensing the software is permitted. For instance, the Android cellphone operating system was initially mostly under permissive open-sources licenses, such as the MIT license (but the Linux kernel was copyleft). Much of the Android operating system has since been re-licensed, and is under a proprietary license (owned by Google).[1] The Linux kernel cannot be re-licensed due to the copyleft. Google's new mobile operating system, Fuchsia, has a new kernel, and all of Fuchsia is under permissive licenses.

Similarly, the abandoned mobile operating system "FirefoxOS" was copied and modified to make "KaiOS". As FirefoxOS was under a permissive license, the license could be changed, and KaiOS was released under a proprietary license. The code is still open-source, because the source code is still published, but modifying it requires the company's permission. See Wikipedia article.

The main players

Lawrence Lessig

Lawrence Lessig is an American lawyer who wrote a book in 2004 called "Free Culture" and founded the Creative Commons organisation, which has popularised some copyleft licenses commonly used on the internet today.

Richard Stallman

Richard Stallman is an American software developer who founded the Free Software Foundation and wrote the GPL (GNU General Public License), the most widely-used open source license for software. The Free Software Foundation designed the GNU Free Documentation License, originally intended to do the same for software documentation (help files etc.) as the GPL does for software itself.

The Free Cultural Works Definition defines four essential requirements for a license to be considered a "Free Culture License" (includes permissive and copyleft licenses):

1. The freedom to use and perform the work
2. The freedom to study the work and apply the information
3. The freedom to redistribute copies
4. The freedom to distribute derivative works

The Wikimedia Foundation (which manages this project, Wikimedia Commons, as well as most famously Wikipedia) is currently one of the largest users (and thus, indirectly advocates) of copyleft licenses. Their licensing policy requires that all projects they manage use "Free Culture Licenses" as defined by the Free Cultural Works definition.

Flickr, a popular photo-sharing website, allows users to easily choose Creative Commons licenses for their photographs. Flickr's popularity has increased awareness and knowledge of the Creative Commons licenses among its users. Flickr's API also helps to encourage re-use of such freely-licensed photographs.

Public domain and approximations

When you release a work into the public domain (or otherwise attempt to renounce all rights to the work), you are giving up all control over the work. In some jurisdictions it may not be legally possible, since moral rights may be unrenounceable, but one can waive rights of exploitation and distribution.

This means that although a public domain work is in one sense "the most free", as it can be used in the widest range of possible uses, derivative works may "become unfree" as the creator of the derivative work can choose to use traditional restrictive licensing.

To ensure that works "stay free", it's necessary to use a work that has a ShareAlike condition.

Copyleft / Sharealike

From "copyright" and the English phrase "share and share alike"; the former usually applied to software, the latter to other works. Prevents work from becoming unfree through relicensing, by forbidding relicenseing, including for derivative works.

Two works under different copyleft licenses usually cannot be combined, unless the licences explicitly say they may. This is often the case for the most common copyleft licenses. It can thus be important to choose a common copyleft license, not an obscure one.

Common license conditions

Compare these to the essential freedoms at http://freedomdefined.org/Definition#Defining_Free_Culture_Licenses :

Name	Explanation	Allowed at Wikimedia Commons?
Permission	Re-users must ask the copyright holder's permission before using the work.	No
Notification	Re-users must notify the copyright holder when they use the work.	No
Fulltext (FT)	Re-users must display the full text of the license every time they use the work.	Yes
Attribution (BY)	Re-users must attribute the work to the copyright holder when they use it.	Yes
ShareAlike (SA)	Re-users who create derivatives of the work must release the derivatives under the same license as the original work, if they choose to distribute the derivatives.	Yes
NonCommercial (NC)	The work can only be used for non-commercial purposes.	No
NoDerivatives (ND)	Re-users are not allowed to distribute derivatives of the work. (Essentially: the work cannot be modified.)	No

Why are some conditions forbidden on Commons?

No-derivative licenses are obviously problematic on a collaborative website. Permission and notification would impose substantial administrative burdens. Wikipedia is used commercially (for instance, there are businesses that sell copies of Wikipedia on memory sticks, or even printed books of articles, to people with no internet connection). It is also not yet clear exactly what the non-commercial license means in law.[2]

Common free licenses

Old versions of licenses

Generally it is recommended to license under the most recent version of a license.

Making life easier for re-users

A license with a FullText requirement can be somewhat unfriendly for reuses in some formats (such as print).

Some collaborative sites already have one or more chosen licenses and all content contributed to the site must conform to this. Users of such sites need material to be available under the same license as the site.

This is why Commons recommends dual-licensing under the GFDL and the CC-BY-SA license (all versions). Both licenses have a ShareAlike restriction, ensuring the work will remain free no matter how it is used or modified. Using 'all versions' of the CC-BY-SA license maximises re-usability for sites which may be "stuck" with an earlier version of the CC-BY-SA license. Using the GFDL ensures the work can be used unquestionably by the vast majority of Wikimedia projects.

See also

• Commons:Copyright tags
• Commons:Multi-licensing
• Commons:Donate to the public domain
• Commons:Enforcing license terms
• Commons:Can I require notification of use of my files?
• Commons:License revocation

Further information

• Definition of Free Cultural Works
• Creative Commons
• Free Software Foundation
• Stanford University Library copyright FAQ