Editing Qt (software) (section)

=== Becoming free software–friendly ===
With the release of version 2.0 of the toolkit in mid-1999, the license was changed to the [[Q Public License]] (QPL), a [[free software]] license, but one regarded by the [[Free Software Foundation]] as incompatible with the GPL. Compromises were sought between KDE and Trolltech whereby Qt would not be able to fall under a more restrictive license than the QPL, even if Trolltech was bought out or went bankrupt. This led to the creation of the KDE Free Qt foundation,<ref>{{cite web |url=https://www.kde.org/community/whatiskde/kdefreeqtfoundation.php|title=KDE Free Qt Foundation}}</ref> which guarantees that Qt would fall under a [[BSD-style license]] should no free/open source version of Qt be released during 12 months.<ref>{{cite web |url=https://www.kde.org/community/whatiskde/kdefreeqt_announcement.php|title=KDE Free Qt Foundation announcement|date=June 1998}}</ref><ref>{{cite web|url=https://www.kde.org/community/whatiskde/Software_License_agreement_2013.pdf|title=Software License Agreement|date=13 April 2013|publisher=Digia}}</ref>

In 2000, Qt/X11 2.2 was released under the GPL v2,<ref>{{cite web|url=http://qt.nokia.com/about/news/archive/00000043 |title=Trolltech offers a choice in licensing with the addition of GPL licensing for the upcoming release of Qt |publisher=Qt.nokia.com |archive-url=https://web.archive.org/web/20120313182431/http://qt.nokia.com/about/news/archive/00000043 |archive-date=13 March 2012|access-date=13 November 2011}}</ref> ending all controversy regarding [[License compatibility|GPL compatibility]].

At the end of 2001, Trolltech released Qt 3.0, which added support for Mac OS X (now known as [[macOS]]). The Mac OS X support was available only in the proprietary license until June 2003, when Trolltech released Qt 3.2 with Mac OS X support available under the GPL.

In 2002, members of the [[KDE on Cygwin]] project began porting the GPL licensed Qt/X11 code base to Windows.<ref>{{cite web |url=http://qtwin.sourceforge.net/qt3-win32/history.php|title=Q../Windows Edition history|date=5 June 2006|archive-url=https://web.archive.org/web/20100731070812/http://qtwin.sourceforge.net/qt3-win32/history.php|archive-date=31 July 2010}}</ref> This was in response to Trolltech's refusal to license Qt/Windows under the GPL on the grounds that Windows was not a free/open source software platform.<ref>[https://marc.info/?l=kde-cygwin&m=104431728920022&w=2 E-mail to the kde-cygwin mailing list] by Chris January, 4 February 2003
</ref><ref>{{cite web |url=http://www.trolltech.com/developer/faqs/noncomm.html |title=Qt Non-commercial FAQ |publisher=Trolltech |archive-url=https://web.archive.org/web/20031005175911/http://www.trolltech.com/developer/faqs/noncomm.html |archive-date=5 October 2003}}</ref> The project achieved reasonable success although it never reached production quality.

This was resolved when Trolltech released Qt 4.0 also for Windows under the GPL in June 2005.<ref>{{cite web |url=https://dot.kde.org/2005/06/28/trolltech-releases-qt-40 |title=Trolltech Releases Qt 4.0 &#124; KDE.news |date=28 June 2005 |publisher=KDE.News |access-date=13 November 2011}}</ref> Qt&nbsp;4 supported the same set of platforms in the free software/open source editions as in the proprietary edition, so it is possible, with Qt 4.0 and later releases, to create GPL-licensed free/open source applications using Qt on all supported platforms. The GPL v3 with special exception<ref>{{cite web |url=http://doc.trolltech.com/4.4/license-gpl-exceptions.html |title=Nokia Corporation Qt GPL Exception Version 1.3 |publisher=Doc.trolltech.com |date=22 July 1999 |access-date=13 November 2011 |archive-url=https://web.archive.org/web/20101003074912/http://doc.trolltech.com/4.4/license-gpl-exceptions.html |archive-date=3 October 2010 |url-status=dead }}</ref> was later added as an added licensing option. The GPL exception allows the final application to be licensed under various GPL-incompatible [[free software license|free software]]/[[open source license|open source]] licenses such as the [[Mozilla Public License]] 1.1.