Q Public License
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It fails the Debian Free Software Guidelines, 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, meaning that products derived from code under both the GPL and the QPL cannot be redistributed.
KDE, a desktop environment for Linux, is based on Qt. 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. Meanwhile, the Free Software Foundation and authors of the GPL objected to the QPL as it was a non-copyleft license incompatible with the GPL. As KDE 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.
Other projects that have adopted the Q Public License, sometimes with a change in the choice of jurisdiction clause, include:
- The OCaml compiler and related tools from Projet Cristal at INRIA
- LibreSource is a versatile collaborative platform provided by artenum and dedicated to collaborative software development
- Jpgraph is a graph generation tool written in PHP that dynamically produces charts and graphs as image files for presentation on websites.
- Hercules, a software implementation of the System/370, ESA/390, and z/Architecture mainframe computer architectures.
- CGAL for versions 3.x. The CGAL library is released under GNU General Public License/LGPL since CGAL version 4.0 (March 2012).
- Tgif switched from a free-of-charge non-commercial license to the Q Public License.
- A choice of venue clause
- Forced distribution to a third party
- Forced blanket license to the original developer
- "Re: Bug#251983: libcwd: QPL license is non-free; package should not be in main". debian-legal mailinglist. 8 June 2004.
- "Various Licenses and Comments about Them". GNU Project.