Licenses

Comparison of Licenses

License	Intended scope	Copyleft	Practical modifiability	Attribution	Related rights	Access control prohibition	Worldwide applicability
Against DRM	Works of art	Normal	No	Copyright notice	Granted	Yes	Exact translations
Creative Commons Attribution	Generic	No	No	Copyright notice	No	Yes	National adaptations
Creative Commons Attribution ShareAlike	Generic	Normal	No	Copyright notice	No	Yes	National adaptations
Design Science License	Generic, optimally science data	Normal	Yes	Copyright notice	No	No	Same license (English version)
Free Art License	Works of art	Normal	No	Yes	No	No	Exact translations (French law)
FreeBSD Documentation License	Documentation	No	No	Copyright notice	No	No	Same license (English version)
GNU Free Documentation License	Documentation	Normal	Yes	Yes	No	Yes	Same license (English version)
GNU Lesser General Public License	Generic, optimally Software	Weak	Yes	Copyright notice	No	No	Same license (English version)
GNU General Public License	Generic, optimally Software	Strong	Yes	Copyright notice	No	Version 3 prohibits "Tivoisation" in certain cases	Same license (English version)
Lizenz für Freie Inhalte	Generic	Normal	No	Yes	No	No	Unknown (license text is German)
MIT License	Software	No	No	Copyright notice	No	No	Same license (English version)

Criteria for choosing a license

We explain hereafter some of the criteria which may influence your choice of a free content license. Those criteria are not inherently good or bad. The importance of each criteria depends on the context (for example the kind of work, or the kind of collaborative process you want to encourage), and on personal preferences.

This list is not meant to be exhaustive. Other aspects may be important, like the clarity of the wording of a license, or the philosophy which is defended by its authors, or whether the license is surrounded by an active community of authors.

Endly, we want to stress that, before choosing a license, you must read the license text carefully. No summary, no matter how attractive or reassuring, can replace detailed understanding of the license itself.

Intended scope

Some licenses strive to be as generic as is humanly (or rather, legally) possible. Others deliberately focus on a specific domain of creation, like software, or documentation. When a license has such a focus, it doesn't mean that it cannot be used for other kinds of works, but that its main area of use (and thus its social recognition as a trustable license) is clearly bounded.

For example, the GNU GPL can be used for many kinds of works, but its main area of recognition is software.

Copyleft

When a work is "copylefted", it means all derived works (even if they mix in other works as well) must be distributed under the same terms (usually the same exact license) as the original work. Conversely, a non-copylefted work can be distributed under different terms, and even be rendered non-free.

Therefore, using a copyleft license pretty much guarantees that users of subsequent works (for example modified copies) will be granted the same essential freedoms. On the other hand, a copyleft license can also limit opportunities for re-use, because most copyleft licenses are not compatible between each other. This is why people sometimes prefer non-copyleft license, depending on the work and the kind of practices they want to encourage.

ShareAlike is a synonym of copyleft in the Creative Commons vocabulary.

Strong copyleft also forbids linking or integration the subject work into larger works/projects that are not also licensed with a license with compatible copyleft terms. Weak copyleft lacks such a 'viral copyleft' requirement.

Practical modifiability

Although all free licenses give you the legal right to modify, not all of them try to specify how modifiability of the work is practically enforced. Requiring modifiability is important, especially for works which can be distributed under a completely opaque format such as software binary code ("object code").

The licenses which require practical modifiability usually define a notion of source code, source data or similar. The GNU FDL defines transparent copies and disallows use of technological protection measures (TPM). The Creative Commons licenses disallow use of TPMs.

Attribution

Requiring attribution means that authorship for the work must be recognized in any circumstances. In the context of derived works (modified copies), this includes the initial as well as subsequent authors and contributors.

It is often stated that all licenses can implicitly require attribution, as they mandate that the copyright notice must be kept intact when distributing copies. By including up-to-date authorship information in the copyright notice, one can indeed forbid subsequent works to erase that information. However, future contributions to the work are not guaranteed to be also credited using such a mechanism; indeed, it is based on the good will of authors (or maintainers) of subsequent works. Having an Attribution requirement prevents this from happening and mandates that all subsequent works have the same policy in mentioning authorship.

Attribution is a double-edged sword, as it may become a heavy burden to list all contributors for projects which imply seamless and massive collaboration (like Wikipedia). For many works it is, however, a reasonable requirement.

Related rights

Related rights concern not the mere copying and modification of the work, but its use in a derived manner: for example, performing the work, displaying it in public or private, broadcasting, webcasting, etc. Related rights exist for various areas of creation (songs, theater...); they often belong to people other than the authors of the work, such as perfomers, producers of phonograms, etc.

Some free content licenses take care to also grant related rights to the recipient of the work. There may even be a copyleft provision which states that related works (interpretations, performances, recordings) must be released under the same license as the work.

Access control prohibition

Some licenses contain a clause, which forbids to control access to the licensed content. In some licenses this clause concerns only the licensee (licensor can use access control systems to forbid not granted rights).

Worldwide applicability

When distributing a free work over the world, it is important to understand how people from other countries will be able to reuse this work.

License writers have adopted three different strategies regarding the internationalization of their licenses:

• same license for everyone: only the original license text (often in English) is given legal value, and translations may be provided purely for information purposes;
• exact translations: translations of the original license text are provided, which all have legal value; those translations have exactly the same clauses and wording as the original text;
• local adaptations: the license is rewritten according to each national legal system.

Attention: some licenses use a specific national law: so you cannot interpret the license through your national law, but through the law specified in the license. For example, Free Art License uses French law (you must pay attention to French law also if the license is written in English, German or other languages).

The two first schemes ensure that everyone is given the same rights. In the third scheme (local adaptations), similarity and equivalence of the different versions should be carefully examined.

According to advocates of the adaptation scheme, licenses must be rewritten in order to cope with the peculiarities of the various legal systems. This position is held by the Creative Commons organization.

According to opponents of the adaptation scheme, having different national versions of a license presents the risk to break trust and interoperability. Also, they stress that the Berne Convention for the Protection of Literary and Artistic Works provides a framework which, with careful drafting, allows to write internationally applicable license texts. This position is held by the Free Software Foundation and by the Free Art License authors.

List of licenses

Against DRM

• current version: 2.0
• author: Free Creations
• reference URL (English): http://www.freecreations.org/Against_DRM2.html
• reference URL (Italian): http://www.freecreations.org/Against_DRM2_it.html
• reference URL (Spanish - Castilian): http://www.freecreations.org/Against_DRM2_es1.html
• reference URL (Spanish - Catalan): http://www.freecreations.org/Against_DRM2_es2.html
• reference URL (French): http://www.freecreations.org/Against_DRM2_fr.html

BSD-like non-copyleft licenses

In parallel with the set of GNU licenses (including the GNU GPL), the free software world evolved a number of very simple non-copyleft licenses. These licenses are so simple that no dedicated text is needed to expose the terms of the license. To reuse such a license, you must take its text and replace the copyright notice with your own. Since these licenses are non-copyleft, changing the license text in such a way does not prevent reuse between works from happening.

Regardless of their wording, these licenses always grant the user very broad rights, including the right to modify and distribute without supplying any source code. Also, their concise wording makes them simple to understand and unambiguous as to their effects.

These licenses are often called "BSD-like" because the first occurence of such a license has been the license under which the Berkeley Software Distribution (one of the first free versions of Unix) was shipped to users.

One should distinguish the original BSD license with its controversial advertising clause from the revised BSD license that does not have the advertising clause.

Creative Commons Attribution

• Aliases: CC-BY
• Current version: 3.0

Creative Commons Attribution ShareAlike

• Aliases: CC-BY-SA
• Current version: 3.0

Design Science License

• Not maintained anymore
• License text (English)

FreeBSD Documentation License

• author: FreeBSD Project
• reference URL: http://www.freebsd.org/copyright/freebsd-doc-license.html

Although especially written for the FreeBSD project, this license shows you how to draft a very simple non-copyleft license for documentation works.

Free Art License

• Aliases: License Arte Libre, FAL, LAL
• Current version: 1.3
• author: Copyleft Attitude
• License text (English, version 1.2)
• License text (French)

GNU Free Documentation License

• Aliases: GNU FDL, GFDL, FDL
• Current version: 1.2
• License text (English)

Invariant sections

Invariant sections are a special provision of the GFDL which, if used, prevent anyone from modifying the parts of the work which are defined as "invariant". The Free Software Foundation finds it useful to protect some special "non-functional" parts of the work, like a statement of intent (the motivation for invariant sections was, allegedly, to prevent the GNU Manifesto to be removed or modified in GNU documentations).

We believe, however, that freedom should apply to all kind of works, and that what is "functional" in one situation can be "artistic" in another - and vice-versa. Consequently, a work using invariant sections to forbid some kinds of modifications to the work cannot be considered completely free.

Unless additional permissions are granted, all FDL works contain unmodifiable sections which aren't called Invariant Sections, such as a copy of the license embedded in the document itself.

GNU General Public License

• Aliases: GNU GPL, GPL
• Current version: 3.0
• Author: Free Software Foundation
• License text (English)

The GNU GPL is, according to various statistics, probably the most used free software license. It was also the first license to implement the concept of copyleft, guaranteeing that "GPL'ed" free software cannot become, or take part in, non-free software.

Although the GPL is primarily intended for software programs, it is worded so as to apply to many different kinds of works. The main condition for the GPL to be applicable to a type of work is that it admits the notion of a preferred form of a work for making modifications to it (be it source code in a computer language, music score notation, digital graphics under a format retaining structure, etc.). For example, there are many occurences of text or graphics released under the GPL.

Lizenz für Freie Inhalte

• Aliases: LFFI
• License Text (German)

AFAIK only used by the german portal neppstar for free music and video. Anyway, it seems to be a valid free license.

MIT License

• author: MIT
• reference URL: http://www.opensource.org/osi3.0/licenses/mit-license.php

This license is arguably the simplest form of the BSD-like licenses for software. All the license, except for the no-warranty statement, is condensed in two short paragraphs.

There are variants, like the current BSD license which has an additional provision forbidding endorsement of derived works using the name of the original authors.

Commentary on non-free licenses

• Essay about the Creative Commons non-commercial restriction