Free software license
From Wikipedia, the free encyclopedia
Free software is software which grants recipients the freedom to modify and redistribute the software. This would normally be prohibited by copyright law, so with free software, the copyright holder must give recipients the explicit permission to do these things. This grant of rights is called a licence, and if the above noted freedoms are included in the grant, the licence is a free software licence.
Put another way, a free software licence is a licence which grants, to the recipients, permissions which remove any ownership issues which would otherwise prevent the software from being free software.
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[edit] FSF-approved free software licences
Free Software Foundation, the group that maintains The Free Software Definition, maintains a list of free software licences.[1] The list distinguishes between free software licences that are compatible or incompatible with the FSF licence of choice, the GNU General Public License, which is a copyleft licence. The list also contains licences which the FSF considers non-free for various reasons. Note that the open source licence list differs slightly, but in almost all cases the definitions apply to the same licences.
- For more details on this topic, see List of FSF approved software licences.
[edit] OSI-approved "open source" licences
Another group, Open Source Initiative, also maintains a list of approved licences.
- For more details on this topic, see List of OSI approved software licences.
[edit] Freedom-preserving restrictions
In order to preserve the freedom to use, study, modify, and redistribute free software, most free software licences carry requirements and restrictions which apply to distributors. There exists an ongoing debate within the free software community regarding the fine line needed between restrictions which preserve freedom and those which reduce it.
[edit] Licence compatibility
Licences of software packages containing contradictory requirements, render it impossible to combine source code from such packages in order to create new software packages.[1]
[edit] Licence proliferation
Licence proliferation compounds the problems of licence incompatibility. It likewise burdens software developers and distributors by increasing the amount of legal documents they must read. Licence 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 licences became more frowned upon.
[edit] Thwarting new attacks
During the 1990s, free software licences 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 GNU GPL[2]. In the decade 2000, tivoisation has emerged as yet another new threat which current free software licences are not protected from.
[edit] Copyleft
Since the mid 1980s, free software licences 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".
[edit] Patent retaliation
Most newly written free software licences since the late 1990s include some form of patent retaliation clauses. These measures ensure that one's rights under the licence (such as to redistribution), may be terminated if one attempts to enforce specific patent monopolies, under noted circumstances, as specified in the licence. 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.
[edit] DRM and Tivoisation
- For more details on this topic, see Tivoisation.
As of late 2006, no free software licences contain explicit language prohibiting additional restrictions being enforced by Digital Restrictions Management (DRM). Current discussion drafts of version 3 GNU GPL do, however, propose to include such specific language in order to deter "Tivoization".
[edit] Attribution, disclaimers and notices
The majority of free software licences require that modified software not claim to be unmodified. Some licences also require that copyright holders be credited. One such example is version 2 GNU GPL, which requires that interactive programs that print warranty or licence information, may not have these notices removed from modified versions intended for distribution.
[edit] Unacceptable restrictions
[edit] 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, or in commercial organisations[3][4][5]. For this reason, the Hacktivismo Enhanced-Source Software License Agreement, and the Spanish SLUC licences are not considered free software by the standards of FSF, OSI, Debian, or the BSD-based distributions.
[edit] BSD philosophy
- For more details on this topic, see Permissive and copyleft licences.
Many users and developers of BSD-based operating systems have a different position on licensing. The main difference is the belief that the copyleft licences, 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 licence does not. Essentially, the BSD licence'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 licence 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 freedom.[2] 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 licence 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 licence without securing the consent of all copyright holders, as the BSD licence 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.
[edit] 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 licence, but FSF disagree. This has very little impact however since the Artistic License is almost always used in a dual-licence 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 licences 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[3] is that the works licensed under the GFDL are considered free as long as they do not contain unmodifiable sections (Invariant Sections).
[edit] See also
[edit] References
- ^ http://www.linuxdevices.com/articles/AT7188273245.html
- ^ http://fsfeurope.org/projects/gplv3/tokyo-rms-transcript.en.html#v1v2
- ^ http://www.gnu.org/licenses/hessla.html
- ^ http://www.fsf.org/blogs/licensing/freeasinbombs
- ^ http://fsfeurope.org/projects/gplv3/barcelona-rms-transcript#q11-banning-bad-use
[edit] External links
- The Free Software Definition (Free Software Foundation).
- The Free Software Foundation's list of free and unfree licenses
- Debian's licence information page
- Open Source Initiative's list of licences
- OpenBSD's "goals" page describes its view of free software
- Transcripts of licence strategy discussions, mostly of Stallman and Moglen, during the drafting of GPLv3
[edit] Online, freely-licensed books and reports
- Understanding Open Source and Free Software Licensing, by Andrew M. St. Laurent
- The Rise of Open Source Licensing, by Mikko Välimäki
- International Open Source Network Free/Open Source Software Licensing - Available as a Wikibook
- Forfás Report on free software business models and licensing (58 pages)
[edit] Non-free, printed publications
- Die GPL kommentiert und erklärt (The GPL commented and explained, in German), by ifrOSS
- Open Source Licensing: Software Freedom and Intellectual Property Law, by Larry Rosen
