Viral license

Viral license is a pejorative name for copyleft licenses, especially the GPL, that allows derivative works only when permissions are preserved in modified versions of the work.[1][2][3][4][5][6] Copyleft licenses include several common open source and free content licenses, such as the GNU General Public License (GPL) and the Creative Commons Attribution-Sharealike license (CC-BY-SA).


The term is most often used to describe the GPL, which requires that any derivative work also be licensed under compatible licenses with the GPL. The viral component is described as such because the licenses spreads a continuing use of the licenses in its derivatives.[7] This can lead to problems when software is derived from two or more sources having incompatible viral licenses in which the derivative work could not be re-licensed at all.[8]

Although the concept is generally associated with licenses that promote free content, proprietary licenses also have viral characteristics. For example, original equipment manufacturer source code software distribution agreements generally grant licensees the right to redistribute copies of the software, but restrict what terms can be in the end user license agreement.[9] However, derivative work is much less common with proprietary licensed work and so the issue of licenses becomes moot.

As an example of viral licensing outside software, after it was revealed that French author Michel Houellebecq plagiarized sections of Wikipedia articles in his novel La Carte et Le Territoire, some commentators said that this automatically made his entire book licensed under the CC-BY-SA Attribution and ShareAlike license.[10]


The term 'General Public Virus' or 'GNU Public Virus' (GPV) as a pejorative name dates back to a year after the GPLv1 was released.[11][12][13][14][15][16] In 2001 Microsoft vice-president Craig Mundie remarked "This viral aspect of the GPL poses a threat to the intellectual property of any organization making use of it."[17] In another context, Steve Ballmer declared that code released under GPL is useless to the commercial sector (since it can only be used if the resulting surrounding code becomes GPL), describing it thus as "a cancer that attaches itself in an intellectual property sense to everything it touches".[18] In response to Microsoft's attacks on the GPL, several prominent Free Software developers and advocates released a joint statement supporting the license.[19]

Criticism of the term

According to Free Software Foundation compliance engineer David Turner, the term viral license creates a misunderstanding and a fear of using copylefted free software.[20] David McGowan has written that there is no reason to believe the GPL could force proprietary software to become free software, but could "try to enjoin the firm from distributing commercially a program that combined with the GPL'd code to form a derivative work, and to recover damages for infringement." If the firm "actually copied code from a GPL'd program, such a suit would be a perfectly ordinary assertion of copyright, which most private firms would defend if the shoe were on the other foot."[21] Richard Stallman has described this view with an analogy, saying, "The GPL's domain does not spread by proximity or contact, only by deliberate inclusion of GPL-covered code in your program. It spreads like a spider plant, not like a virus."[22]


Popular copyleft licenses, such as the GPL, have a clause allowing components to interact with non-copyleft components as long as the communication is abstract, such as executing a command-line tool with a set of switches or interacting with a Web server.[23] As a consequence, even if one module of an otherwise non-copyleft product is placed under the GPL, it may still be legal for other components to communicate with it normally. This allowed communication may or may not include reusing libraries or routines via dynamic linking — some commentators say it does,[24] the FSF asserts it does not and explicitly adds an exception allowing it in the license for the GNU Classpath re-implementation of the Java library.

The interoperability clauses are often pragmatically inoperative due to the vigorous enforcement and strict interpretation of the GPL as it related to integration, aggregation, and linking. It is argued that most forms of incorporation, aggregation, or connectivity with GPL-licensed code is a derivative work that must be licensed under the GPL. In recent years, a number of communities using GPL incompatible licenses have dropped efforts and support for interoperability with GPL-licensed products in response to this trend. Some developers and communities have switched to the GPL or a GPL compatible license in response, which critics and supporters alike agree is intentional end result.

See also


  1. "Microsoft license spurns open source - CNET News". Retrieved 2015-05-30.
  2. Geere, Duncan (2011-12-16). "Some rights reserved: the alternatives to copyright (Wired UK)". Retrieved 2015-05-30.
  3. "Glossary". Retrieved 2015-05-30.
  4. "Inoculating Your Purchase – Contractual Protection from Viral Licenses in M&A Transactions" (PDF). Retrieved 2015-05-30.
  5. Archived 16 March 2015 at the Wayback Machine.
  6. New Media Rights (2008-09-12). "Open Source Licensing Guide". California Western School of Law. Retrieved 2015-11-28. The GPL license is ‘viral,’ meaning any derivative work you create containing even the smallest portion of the previously GPL licensed software must also be licensed under the GPL license.
  7. Golden, Bernard (2005). "3". Succeeding with Open Source. Addison-Wesley. p. 44. ISBN 978-0-321-26853-2.
  8. Nikolai Bezroukov (2000). "Comparative merits of GPL, BSD and Artistic licences (Critique of Viral Nature of GPL v.2 - or In Defense of Dual Licensing Idea)". Archived from the original on 2001-12-22. Viral property stimulates proliferation of licenses and contributes to the "GPL-enforced nightmare" -- a situation when many other licenses are logically incompatible with the GPL and make life unnecessary difficult for developers working in the Linux environment (KDE is a good example here, Python is a less known example).
  9. Meeker, Heather J. (2008). "2". The Open Source Alternative. John Wiley and Sons. p. 11. ISBN 978-0-470-19495-9.
  10. "French Author Plagiarizes Wikipedia; Does That Mean His Entire Book Is Now CC Licensed?". 2010-11-29. Retrieved 2015-05-30.
  11. Vixie, Paul (6 March 2006). "Re: Section 5.2 (IPR encumberance) in TAK rollover requirement draft". IETF Namedroppers mailing list. Archived from the original on 27 September 2007. Retrieved 29 April 2007.
  12. "General Public Virus". Jargon File 2.2.1. 15 December 1990. Retrieved 29 April 2007.
  13. Hackvän, Stig (September 1999). "Reverse-engineering the GNU Public Virus — Is copyleft too much of a good thing?". Linux Journal. Retrieved 29 April 2007.
  14. Stewart, Bill (8 October 1998). "Re: propose: `cypherpunks license' (Re: Wanted: Twofish source code)". Cypherpunks mailing list. Retrieved 29 April 2007.
  15. Buck, Joe (10 October 2000). "Re: Using of parse tree externally". GCC mailing list. Retrieved 29 April 2007.
  16. Griffis, L. Adrian (15 July 2000). "The GNU Public Virus". Retrieved 29 April 2007.
  17. Mundie, Craig (3 May 2001). "Speech Transcript - Craig Mundie". New York University Stern School of Business. Retrieved 23 August 2008.
  18. Newbart, Dave (1 June 2001). "Microsoft CEO takes launch break with the Sun-Times". Chicago Sun-Times. Archived from the original on 15 June 2001. (Internet archive link)
  19. Wikisource link to Free Software Leaders Stand Together. Wikisource.
  20. Byfield, Bruce (29 August 2006). "IT Manager's Journal: 10 Common Misunderstandings About the GPL". Retrieved 23 August 2008.
  21. David McGowan (2005), "Legal Aspects of Free and Open Source Software", in Joseph Feller; Brian Fitzgerald; Scott A. Hissam; Karim R. Lakahani, Perspectives on Free and Open Source Software, MIT Press, p. 382, ISBN 0-262-06246-1
  22. Poynder, Richard (21 March 2006). "The Basement Interviews: Freeing the Code". Retrieved 5 February 2010.
  23. "Frequently Asked Questions about the GNU Licenses". Free Software Foundation. 24 June 2008. Retrieved 23 August 2008.
  24. Raymond, Eric Steven (9 November 2002). "Licensing HOWTO". Retrieved 21 March 2010.
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