लेखाधिकार

The license Wikipedia uses grants free access to our content in the same sense as free software is licensed freely. This principle is known as copyleft. That is to say, Wikipedia content can be copied, modified, and redistributed so long as the new version grants the same freedoms to others and acknowledges the authors of the Wikipedia article used (a direct link back to the article satisfies our author credit requirement).  Wikipedia articles therefore will remain free forever and can be used by anybody subject to certain restrictions, most of which serve to ensure that freedom.

To fulfill the above goals, the text contained in Wikipedia is licensed to the public under the GNU Free Documentation License (GFDL). The full text of this license is at Wikipedia:Text of the GNU Free Documentation License. 

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts.
A copy of the license is included in the section entitled "GNU Free Documentation License".
Content on Wikipedia is covered by disclaimers.

The English text of the GFDL is the only legally binding document; what follows is our interpretation of the GFDL: the rights and obligations of users and contributors.

IMPORTANT:  If you want to use content from Wikipedia, first read the Users' rights and obligations section.  You should then read the GNU Free Documentation License.

 Users' rights and obligations 

If you want to use Wikipedia materials in your own books/articles/web sites
or other publications, you can do so, but you have to follow the GFDL. If you are simply duplicating the Wikipedia article, you must follow section two of the GFDL on verbatim copying, as discussed at Wikipedia:Verbatim copying.

If you create a derivative version by changing or adding content, this entails the following:
 your materials in turn have to be licensed under GFDL,
 you must acknowledge the authorship of the article (section 4B), and
 you must provide access to the "transparent copy" of the material (section 4J). (The "transparent copy" of a Wikipedia article is any of a number of formats available from us, including the wiki text, the html web pages, xml feed, etc.) 

You may be able to partially fulfill the latter two obligations by providing a conspicuous direct link back to the Wikipedia article hosted on this website. You also need to provide access to a transparent copy of the new text. However, please note that the Wikimedia Foundation makes no guarantee to retain authorship information and a transparent copy of articles. Therefore, you are encouraged to provide this authorship information and a transparent copy with your derived works.

 Example notice 

An example notice, for an article that uses the Wikipedia article Metasyntactic variable might read as follows:

 This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Metasyntactic variable".

("Metasyntactic variable" and the Wikipedia URL must of course be substituted accordingly.)

Alternatively you can distribute your copy of "Metasyntactic variable" along with a copy of the GFDL (as explained in the text) and list at least five (or all if fewer than five) principal authors on the title page (or top of the document).  The external Page History Stats tool can help you identify the principal authors.

 Fair use materials and special requirements 
All original Wikipedia text is distributed under the GFDL. Occasionally, Wikipedia articles may include images, sounds, or text quotes used under the U.S. Copyright law "fair use" doctrine. It is preferred that these be obtained under the most free (libre) license (such as the GFDL or public domain) practical. In cases where no such images/sounds are currently available, then fair use images are acceptable (until such time as free images become available). 

In Wikipedia, such "fair use" material should be identified as from an external source (on the image description page, or history page, as appropriate). This also leads to possible restrictions on the use, outside of Wikipedia, of such "fair use" content retrieved from Wikipedia: this "fair use" content does not fall under the GFDL license as such, but under the "fair use" (or similar/different) regulations in the country where the media are retrieved.

Wikipedia does use some text under licenses that are compatible with the GFDL but may require additional terms that we do not require for original Wikipedia text (such as including Invariant Sections, Front-Cover Texts, or Back-Cover Texts). When wanting to contribute such texts that include Invariant Sections or Cover Texts to Wikipedia, see Introducing invariant sections or cover texts in Wikipedia below.

 Image guidelines 

Images and photographs, like written works, are subject to copyright.  Someone owns them unless they have been explicitly placed in the public domain.  Images on the internet need to be licensed directly from the copyright holder or someone able to license on their behalf.  In some cases, fair use guidelines may allow a photograph to be used.
 Tagging 

Image description pages can be tagged with a special tag to indicate the legal status of the images, as described at Wikipedia:Image copyright tags. It is currently unclear what should happen in cases where the same image has been uploaded more than once with different respective copyright statements.

 U.S. government photographs 

Works produced by civilian and military employees of the United States federal government in the scope of their employment are public domain by statute. However, note that, despite popular misconception, the U.S. Federal Government can own copyrights that are assigned to it by others (for example, works created by contractors).  Be careful, however: not all images on .mil and .gov websites are public domain. Among other reasons, the site may be using commercial stock photography owned by others. It may be useful to check the privacy and security notice of the website, but only with an email to the webmaster can you be confident that an image is in the public domain. It should also be noted that governments outside the U.S. often do claim copyright over works produced by their employees (for example, Crown Copyright in the United Kingdom). Also, most state and local governments in the United States do not place their work into the public domain and do in fact own the copyright to their work. Please be careful to check ownership information before copying.

 UK Crown Copyright 
The UK Office of Public Sector Information, formerly HMSO, has told us:
 Crown copyright protection in published material lasts for fifty years from the end of the year in which the material was first published.  Therefore [for example] material published [fifty-one years ago], and any Crown copyright material published before that date, would now be out of copyright, and may be freely reproduced throughout the world. 

 Celebrity photographs 

This is based on the image guidelines at IMDB, so it especially applies to celebrity photographs, but also can apply to other pictures.  Legitimate photographs generally come from three different places with permission.

 The studios, producers, magazine publisher, or media outlet that originally shot the photograph.
 Agencies that represent the photographers who shot the photos or the photographer themself (the latter especially for amateur photographs)
 Submissions from the celebrity himself or herself or a legal representative of the celebrity.

 Comments on copyright laws by country 

Russia: copyright exemptions 
According to the Russian copyright law of 1993 (Федеральный закон от 9.07.1993 № 5351-1), the following items are not subject to copyrights:
Official documents (laws, court decisions, other texts of legislative, administrative or judicial character);
State symbols and tokens (flags, coats of arms, orders, banknotes and other state symbols and tokens);
Folk creative works;
Reports about events and facts, of informative character.

Russian copyrights generally expire in 70 years after the death of the author. Items by authors who died prior to 1953 are public domain, because the expiration term was 50 years before 2004, and this change of the term wasn't retroactive, according to Law 72-FZ, 2004 (in Russian), article 2, part 3). 

If an item was not published during author's life, its copyright expire in 70 years after its first lawful publication (if the item wasn't moved into PD before). This gives maximum term for unpublished or posthumously published works of 140 (if the author died after 1953) or 120 years (if the author died before 1953, AND his work was published before 2003).

If an item was published anonymously or pseudonymously, and its author remains unknown, its copyright expires in 70 years after its first lawful publication. If the author is discovered, usual rule applies.

PD status of a work in Russia can differ with that in the US, where Wikipedia servers are located.

Algeria

Article 9 of Algeria's Ordonnance N°97-10 du 27 Chaoual 1417 correspondant au 6 mars 1997 relative aux droits d'auteur et aux droits voisins. states that: "Works of the State made licitly accessible to the public may be freely used for non-profit purposes, subject to respect for the integrity of the work and indication of its source.  By "works of the State", in this article, are meant works produced and published by the various organs of the State, local communities, or public establishments of an administrative character." (original is in French.)  In short, they are available for non-commercial use - which is deprecated on Wikipedia.

Iran
Although there has been no treaty between Iran and the United States regarding copyright protection, according to Jimbo Wales, Wikipedia contributors should respect Iranian copyright law as best they can, the same as they do for other countries around the world. 

 Contributors' rights and obligations 

If you contribute material to Wikipedia, you thereby license it to the public
under the GFDL (with no invariant sections, front-cover texts, or back-cover
texts).
In order to contribute, you therefore must be in a position to grant this
license, which means that either
 you own the copyright to the material, for instance because you produced it yourself, or
 you acquired the material from a source that allows the licensing under GFDL, for instance because the material is in the public domain or is itself published under GFDL.

In the first case, you retain copyright to your materials. You can later republish and relicense them in any way you like. However, you can never retract the GFDL license for the versions you placed here: that material will remain under GFDL forever.

In the second case, if you incorporate external GFDL materials, as a requirement of the GFDL, you need to
acknowledge the authorship and provide a link back to the network location of the original copy.

Introducing invariant sections or cover texts in Wikipedia
Under Wikipedia's current copyright conditions, and with the current facilities of the MediaWiki software, it is only possible to include in Wikipedia external GFDL materials that contain invariant sections or cover texts, if all of the following apply,
 You are the copyright holder of these external GFDL materials (or: you have the explicit, i.e. written, permission of the copyright holder to do what follows);
 The length and nature of these invariant sections and cover texts does not exceed what can be placed in an edit summary;
 You are satisfied that these invariant sections and cover texts are not listed elsewhere than in the "page history" of the page where these external materials are placed;
 You are satisfied that further copies of Wikipedia content are distributed under the standard GFDL application of "with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts" (in other words, for the copies derived from wikipedia, you agree that these parts of the text contributed by you will no longer be considered as "invariant sections" or "cover texts" in the GFDL sense);
 The original invariant sections and/or cover texts are contained in the edit summary of the edit with which you introduce the thus GFDLed materials in wikipedia (so, that if "permanent deletion" would be applied to that edit, both the thus GFDLed material and its invariant sections and cover texts are jointly deleted).
Seen the stringent conditions above, it is very desirable to replace GFDL texts with invariant sections (or with cover texts) by original content without invariant sections (or cover texts) whenever possible.

 Using copyrighted work from others 

If you use part of a copyrighted work under "fair use", or if you obtain special permission to use a copyrighted work from the copyright holder under the terms of our license, you must make a note of that fact (along with names and dates). It is our goal to be able to freely redistribute as much of Wikipedia's material as possible, so original images and sound files licensed under the GFDL or in the public domain are greatly preferred to copyrighted media files used under fair use. See Wikipedia:Boilerplate request for permission for a form letter asking a copyright holder to grant us a license to use their work under terms of the GFDL. 

Never use materials that infringe the copyrights of others.
This could create legal liabilities and seriously hurt the project.
If in doubt, write it yourself.

Note that copyright law governs the creative expression of ideas, not the ideas or information themselves.  Therefore, it is legal to read an encyclopedia article or other work, reformulate the concepts in your own words, and submit it to Wikipedia.  However, it would still be unethical (but not illegal) to do so without citing the original as a reference.  See plagiarism and fair use for discussions of how much reformulation is necessary in a general context.

 Linking to copyrighted works 

Linking to copyrighted works is usually not a problem, as long as you have made a reasonable effort to determine that the page in question is not violating someone else's copyright. If it is, please do not link to the page. Whether such a link is contributory infringement is currently being debated in the courts, but in any case, linking to a site that illegally distributes someone else's work sheds a bad light on us. If the site in question is making fair use of the material, linking is OK.

 If you find a copyright infringement 

It is not the job of rank-and-file Wikipedians to police content for possible copyright infringement, but if you suspect one, you should at the very least bring up the issue on that page's talk page. Others can then examine the situation and take action if needed. The most helpful piece of information you can provide is a URL or other reference to what you believe may be the source of the text.

Some cases will be false alarms. For example, if the contributor was in fact the author of the text that is published elsewhere under different terms, that does not affect their right to post it here under the GFDL. Also, sometimes you will find text elsewhere on the Web that was copied from Wikipedia. In both of these cases, it is a good idea to make a note in the talk page to discourage such false alarms in the future.

If some of the content of a page really is an infringement, then the infringing content should be removed, and a note to that effect should be made on the talk page, along with the original source. If the author's permission is obtained later, the text can be restored.

If all of the content of a page is a suspected copyright infringement, then the page should be listed on Wikipedia:Copyright problems and the content of the page replaced by the standard notice which you can find there. If, after a week, the page still appears to be a copyright infringement, then it may be deleted following the procedures on the votes page.

In extreme cases of contributors continuing to post copyrighted material after appropriate warnings, such users may be blocked from editing to protect the project.

 See also 
 Wikipedia:Copyright FAQ
 The Wikipedia:Contributing FAQ for questions on copyright.
 Wikipedia's designated agent under OCILLA
 Wikipedia:Sites that use Wikipedia as a source
 Wikipedia:Standard GFDL violation letter
 Wikipedia:Possible copyright infringements
 Wikipedia:Spotting possible copyright violations
 Wikipedia:Fair use
 Wikipedia:Image copyright tags
 Wikipedia:Boilerplate request for permission

Further discussion...
 Wikipedia:Copyright issues
 m:Wikipedia and copyright issues
 m:Avoid Copyright Paranoia
 m:Permission grant extent