Free-software license: Difference between revisions

Revision as of 22:01, 25 July 2007

A free-software license is a software license which grants recipients rights to modify and redistribute the software which would otherwise be prohibited by copyright law. A free-software license grants, to the recipients, freedoms in the form of permissions to modify or distribute copyrighted work.

History

There is no recognised "first" free-software license. Early licenses include that of TeX and that of X11.

In the mid-80s, the GNU project produced individual free-software licenses for each of its software packages. These were all replaced in 1989 with version 1 of the GNU General Public License (GPL). Version 2 of the GPL, released in 1991, went on to become the most widely used free-software license.

In the mid- to late-90s, a trend began where companies and new projects wrote new licenses. This license proliferation lead to problems of complexity and incompatibility. The trend slowed, and reversed in some ways, in the early 2000s.

FSF-approved free-software licenses

Free Software Foundation, the group that maintains The Free Software Definition, maintains a list of free-software licenses.^[1] The list distinguishes between free-software licenses that are compatible or incompatible with the FSF license of choice, the GNU General Public License, which is a copyleft license. The list also contains licenses which the FSF considers non-free for various reasons.

OSI-approved "open source" licenses

Another group, Open Source Initiative (OSI), also maintains a list of approved licenses. OSI and FSF agree on all widely used free-software licenses. OSI's list is different from FSF's list because the two organisations have reviewed different sets of licenses. There are a few licenses that OSI have approved that FSF rejected, and vice versa, but these are licenses that are used by niche projects or none at all.

Restrictions

In order to preserve the freedom to use, study, modify, and redistribute free software, most free-software licenses carry requirements and restrictions which apply to distributors. There exists an ongoing debate within the free software community regarding the fine line between restrictions which preserve freedom and those which reduce it.

During the 1990s, free-software licenses began including clauses, such as patent retaliation, in order to protect against software patent litigation cases which had not previously existed. This new threat became the primary purpose for composing the new version 2 of the GNU GPL.^[2] In the decade 2000, tivoisation has emerged as yet another new threat which current free-software licenses are not protected from.

Copyleft

Since the mid 1980s, free-software licenses written by Richard Stallman pioneered a concept known as copyleft. Ensuing copyleft provisions stated that modified versions of free software must be distributed under the same terms as the original software. Thus, all enhancements and additions to copylefted software must also be distributed as free software. This is sometimes referred to as "share and share alike" or "quid pro quo".

Patent retaliation

Most newly written free-software licenses since the late 1990s include some form of patent retaliation clauses. These measures ensure that one's rights under the license (such as to redistribution), may be terminated if one attempts to enforce specific patent monopolies, under noted circumstances, as specified in the license. As an example, the Apple Public Source License may terminate a user's rights if said user embarks on litigation proceedings against them due to patent litigation. Patent retaliation emerged in response to proliferation and abuse of software patents.

Tivoisation

As of late 2006, no free-software licenses contain explicit language prohibiting additional restrictions being enforced by digital rights management (DRM). Version 3 of the GNU GPL does, however, include such specific language in order to prohibit "Tivoisation" in certain cases.

Attribution, disclaimers and notices

The majority of free-software licenses require that modified software not claim to be unmodified. Some licenses also require that copyright holders be credited. One such example is version 2 GNU GPL, which requires that interactive programs that print warranty or license information, may not have these notices removed from modified versions intended for distribution.

Practical problems that licenses try to avoid

license compatibility

licenses of software packages containing contradictory requirements, render it impossible to combine source code from such packages in order to create new software packages.^[3]

For example, if one license says "modified versions must mention the developers in any advertising materials", and another license says "modified versions cannot contain additional attribution requirements", then, if someone combined a software package which uses one license with a software package which uses the other, it would be impossible to distribute the combination because the two requirements cannot be simultaneously fulfilled. Thus, these two packages would be license-incompatible.^[4]

license proliferation

license proliferation compounds the problems of license incompatibility. It likewise burdens software developers and distributors by increasing the amount of legal documents they must read. license proliferation gained momentum during the late 1990s and increased into the early 2000s. By the year 2005, it was being identified as a problematic phenomenon and the gratuitous writing of new licenses became more frowned upon.

Unacceptable restrictions

Purpose of use

Restrictions on private use of the software ("use restrictions") are generally unacceptable. Examples include prohibiting the software to be used for military purposes, for comparison or benchmarking, for ethically-questionable means,^[5] or in commercial organisations.^[6] For this reason, such licenses are not considered free software by the standards of the FSF, OSI, Debian, or the BSD-based distributions.

BSD philosophy

Many users and developers of BSD-based operating systems have a different position on licensing. The main difference is the belief that the copyleft licenses, particularly the GNU General Public License (GPL), are too complicated and have restrictions which are undesirable. The GPL requires derivative work to be released according to the GPL while the BSD license does not. Essentially, the BSD license's only requirement is to acknowledge the original authors, and poses no restrictions on how the source code may be used. As a result, BSD code can find its way into proprietary software that only acknowledge the source. For instance, the IP stack in Microsoft Windows and Mac OS X are derived from BSD-licensed software.

GPL supporters claim that mandating derivative works remain free fosters the growth of free software and requires equal participation by all users. Developers who use GPL code have to share their improvements with the community, supporting the growth of the software they received.

Supporters of the BSD license argue that it is more free than the GPL because it grants the right to do anything with the source code, second only to software in the public domain. The nature of BSD has encouraged the inclusion of well-developed standard code into proprietary software. In response, GPL supporters claim that this is more a form of power than a necessary freedom.^[7] The right to make closed-source code is therefore not included in the Free Software Foundation's "four freedoms of free software"; using, studying, copying, and distributing modifications of the code.

Code licensed under the BSD license can be relicensed under the GPL (is "GPL-compatible") without securing the consent of all original authors. Code under the GPL cannot be relicensed under the BSD license without securing the consent of all copyright holders, as the BSD license is not copyleft and therefore GPL is "BSD-incompatible". Existing free software BSDs tend to avoid including software licensed under the GPL in the core operating system, or the base system, except as a last resort when alternatives are non-existent or vastly less capable, such as with GCC. The OpenBSD project has acted to remove GPL-licensed tools in favour of BSD-licensed alternatives, some newly written and some adapted from older code.

Debian

The Debian project uses the criteria laid out in its Debian Free Software Guidelines (DFSG). The only notable cases where Debian and Free Software Foundation disagree are over the Artistic License and the GNU Free Documentation License. Debian accept the original Artistic License as being a free-software license, but FSF disagree. This has very little impact however since the Artistic License is almost always used in a dual-license setup, along with the GNU General Public License.

Regarding the GNU Free Documentation License, Debian argues that the DFSG applies to documentation as it does on software, and so documentation licenses must be examined against these free software guidelines. FSF say that documentation is qualitatively different from software and is subject to different requirements. The end result of a long discussion and the eventual vote in Debian ^[8] is that the works licensed under the GFDL are considered free as long as they do not contain unmodifiable sections (what the GFDL calls "Invariant Sections").

External links

References

^ http://www.fsf.org/licensing/licenses/index_html
^ http://fsfeurope.org/projects/gplv3/tokyo-rms-transcript.en.html#v1v2
^ http://www.linuxdevices.com/articles/AT7188273245.html
^ "Stallman explains license compatibility while discussing GPLv3". {{cite web}}: Cite has empty unknown parameter: |1= (help)
^ http://www.gnu.org/licenses/hessla.html
^ http://fsfeurope.org/projects/gplv3/barcelona-rms-transcript#q11-banning-bad-use
^ "Freedom or Power? by Bradley Kuhn and Richard Stallman". {{cite web}}: Cite has empty unknown parameter: |1= (help)
^ "Debian vote on allowing GFDL'd works into their distro". {{cite web}}: Cite has empty unknown parameter: |1= (help)

[1] ttp://www.fsf.org/licensing/licenses/index_html

[2] ttp://fsfeurope.org/projects/gplv3/tokyo-rms-transcript.en.html#v1v2

[3] ttp://www.linuxdevices.com/articles/AT7188273245.html

[4] "Stallman explains license compatibility while discussing GPLv3". {{cite web}}: Cite has empty unknown parameter: |1= (help)

[5] ttp://www.gnu.org/licenses/hessla.html

[6] ttp://fsfeurope.org/projects/gplv3/barcelona-rms-transcript#q11-banning-bad-use

[7] "Freedom or Power? by Bradley Kuhn and Richard Stallman". {{cite web}}: Cite has empty unknown parameter: |1= (help)

[8] "Debian vote on allowing GFDL'd works into their distro". {{cite web}}: Cite has empty unknown parameter: |1= (help)

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Revision as of 19:03, 25 July 2007 edit Stevenj (talk \| contribs) Extended confirmed users 14,829 edits make hyphenation and spelling consistent with title (when "free software" is used as a compound adjective, good English style suggests that it should be hyphenated) ← Previous edit	Revision as of 22:01, 25 July 2007 edit undo Watch37264 (talk \| contribs) 3,891 edits m moved Free-software license to Free-software licence: Revert changing of title between varieties of English Next edit →
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