The Q Public License (QPL) is a copyleft license created by Trolltech for its free edition of the Qt toolkit. It captures the general meaning of the GNU General Public Licence (GPL), but is incompatible with it, meaning that you cannot legally distribute products based on both GPL'ed and QPL'ed code.

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 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. The GPL states that it must always continue to be under that license. KDE immediately chose the GPL.

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

External links

• A copy of the license.