From Wikipedia, the free encyclopedia.
The Q Public License (QPL) is a non-copyleft license created by Trolltech for its free edition of the Qt toolkit. It captures the general meaning of the GNU General Public Licence about the derivatives for non commercial use, but it prohibits the commercial use of derivatives.
But it also allowed Qt to change the license in later editions of its software, something not provided in the GPL, and it was also frowned-upon that commercial use or development of derivatives was still not allowed. (The QPL was only for the personal edition of QT; the commercial edition (which is exactly the same) is under a pay-per-use license and couldn't be freely distributed.) As KDE, a desktop environment for Linux based on Qt, grew in popularity, the free software community urged Qt to put it under a license that would assure that Qt would be open source forever and could be used and developed by companies. Eventually, under pressure, Qt said that it could be used under the terms of the GPL or the QPL. The GPL says that it must always continue to be under that license. KDE immediately chose the GPL.