Q Public License

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The Q Public License (QPL) is a non-copyleft license, created by Trolltech for its free edition of the Qt. It is incompatible with the GPL, meaning that you cannot legally distribute products derived from both GPL'ed and QPL'ed code. It was used until Qt 3.0, as Trolltech toolkit version 4.0 was released under GPL version 2. It fails the Debian Free Software Guidelines[1] used by several Linux distributions, though it qualifies for the Free Software Foundation's Free Software Definition; however, it is not compatible with the FSF's GNU General Public License.[2]

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Opposition to the license

The Free Software Foundation, authors of the GPL, sum up their objections to the QPL [2]:

It also allowed Qt to change the license in later editions of its software, something often also provided in the GPL, and it was also frowned upon that non-free use or development of derivatives was still not allowed. Only the personal edition of Qt was covered by the QPL; the commercial edition, which is functionally equal, is under a pay-per-use license and could not be freely distributed. As KDE, a desktop environment for Linux based on Qt, grew in popularity, the free software community urged Trolltech to put Qt under a license (the QPL) that would assure that it would remain free software forever and could be used and developed by commercial third-parties. Eventually, under pressure, Trolltech dual-licensed Qt for use under the terms of the GPL or the QPL.

All legal disputes about the license are settled in Oslo, Norway, but it has never been legally contested.

The Debian project rejects software covered by solely QPL[1] (and not dual licensed with something else like the GPL) because of:

  • a choice of venue clause
  • forced distribution to a third party
  • forced blanket license to the original developer

Adoption of the license

Other projects that have adopted the Q Public License, sometimes with a change in the choice of jurisdiction clause, include:

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