Editing Free software movement (section)

=== "Viral" copyleft licensing ===
The free software movement champions [[copyleft]] licensing schema (often pejoratively called "[[viral license]]s"). In its strongest form, copyleft mandates that any works ''derived'' from copyleft-licensed software must also carry a copyleft license, so the license spreads from work to work like a computer virus might spread from machine to machine. Stallman has previously stated his opposition to describing the [[GNU GPL]] as "viral". These licensing terms can only be enforced through asserting copyrights.<ref>{{Citation
 | author = David McGowan
 | chapter = Legal Aspects of Free and Open Source Software
 | title = Perspectives on Free and Open Source Software
 |editor1=Joseph Feller |editor2=Brian Fitzgerald |editor3=Scott A. Hissam |editor4=Karim R. Lakahani | publisher = MIT Press
 | year = 2005
 | isbn = 0-262-06246-1
 | page = 382}}</ref>

Critics of copyleft licensing challenge the idea that restricting modifications is in line with the free software movement's emphasis on various "freedoms", especially when alternatives like [[MIT License|MIT]], [[BSD Licenses|BSD]], and [[Apache License|Apache]] licenses are more permissive.<ref>{{cite web|title=Open Source Licensing Guide|url=http://www.newmediarights.org/open_source/new_media_rights_open_source_licensing_guide|website=New Media Rights|access-date=13 February 2015|archive-date=13 February 2015|archive-url=https://web.archive.org/web/20150213052820/http://www.newmediarights.org/open_source/new_media_rights_open_source_licensing_guide|url-status=live}}</ref><ref>{{cite news
| first=Dave
| last=Newbart
| title=Microsoft CEO takes launch break with the Sun-Times
| date=2001-06-01
| newspaper=Chicago Sun-Times
| url=http://suntimes.com/output/tech/cst-fin-micro01.html
| archive-url=https://web.archive.org/web/20010615205548/http://suntimes.com/output/tech/cst-fin-micro01.html
| archive-date=2001-06-15
}}(Internet archive link)</ref> Proponents enjoy the assurance that copylefted work cannot usually be incorporated into non-free software projects.<ref>
{{Cite book
 |author1=Kirk St.Amant  |author2=Brian Still
  |name-list-style=amp | chapter = Examining Open Source Software Licenses through the Creative Commons Licensing Model
 | title = Handbook of Research on Open Source Software: Technological, Economic, and Social Perspectives
 | publisher = Information Science Reference
 | year = 2008
 | pages = 382 of 728
 | isbn = 978-1-59140-999-1}}</ref> They emphasize that copyleft licenses may not attach for all uses and that in any case, developers can simply choose not to use copyleft-licensed software.<ref>{{cite web |url=http://www.linuxtoday.com/developer/2006082902126OSHLLL |title=IT Manager's Journal: 10 Common Misunderstandings About the GPL |first=Bruce |last=Byfield |date=2006-08-29 |access-date=2008-08-23 |archive-date=2020-02-16 |archive-url=https://web.archive.org/web/20200216180035/https://www.linuxtoday.com/developer/2006082902126oshlll |url-status=live }}</ref><ref>{{cite web
| last=Poynder
| first=Richard
| title=The Basement Interviews: Freeing the Code
| date=21 March 2006
| access-date=5 February 2010
| url=https://archive.org/stream/The_Basement_Interviews/Richard_Stallman_Interview_djvu.txt
}}</ref>