QPL

The Public License Q ( QPL ) is a license created by Trolltech for the free version of its software library Qt. It includes the general terms of the public License general GNU (GNU LPG) but is incompatible with this one: one cannot legally distribute a product resulting from codes LPG and QPL.

The principal difference between the LPG and the QPL is that the QPL forces the developer to provide its source code if it is of any manner related to a code QPL (a library, for example), even if this code QPL is not distributed with the software of the developer. It is the principal difference with license LPG, as well as the main reason which makes that Qt is QPL and not LPG. That means that code which uses Qt under license QPL must be distributed under the conditions of the QPL and provide the source code.

The Free Software Foundation, author of the LPG, summarizes its objections with the QPL thus:

It acts of a license of free software which is not Copyleft and which is not compatible with GNU LPG. It causes of more than important practical nuisances, because the modified sources can be distributed only in the form of patchs.

We recommend to you to avoid using the QPL for no matter what you write, and to use the parcellings only in the event of absolute need. Nevertheless, this recommendation does not apply to Qt itself any more, since Qt is now also provided under GNU LPG.

Since the QPL is incompatible with GNU LPG, it is not possible to use a program under QPL and another under GNU LPG and to bind them one to the other.

Cependant, if you wrote a program using a library covered by the QPL (called FOO) and that you want to distribute this program under the LPG of GNU, there it is possible without problem. For your program, the conflict can be solved by the addition of a note such as this one:

On a purely completely exceptional basis, you have the right to bind

this program to library FOO and to distribute des" of it;

achievable on the condition of following the recommendations

of the LPG of GNU with regard to the totality of the software

and of its achievable others that FOO.

Légalement you have the right to make it provided that you are well holder of the royalties on this program. Unite this note with the source files, following the text explaining that the program is covered by the LPG of GNU.

It should be noted that the incompatibility between the QPL and the LPG comes from the character contaminant from the LPG which authorize only but work derived under license LPG. From this point of view the QPL is more permissive than the LPG, and is located " entre" LPG and the LGPL.
The QPL is a license of European right. All the legal conflicts on this license gather with Oslo. It legally disputed forever.
FSF also made it possible Qt to modify the license in its last versions, possibility often also provided by the LPG, and disapproved the fact that the nonfree use or the development of derived was still not authorized. Only the personal version of Qt is covered by the QPL; the commercial release, which is functionally equivalent, is under a license which imposes the payment with use and cannot be distributed freely. The economic model set up by Trolltech is based on a double licencing (an open version free source and a paying commercial release authorizing integration in code owner, with distinctions between system of exploitation". The base of code is identical in both cases. This model is rather close to what can be made with a model of centralization of the intellectual property laws (like does it for certain one its projects) and a diffusion under license LPG. Distinction concerned with the vulnerability of the initial community vis-a-vis a fork, induced for example by a more powerful industrial competitor.
Once the maturity of the communities and know-how recognized, it is natural to evolve to models containing/. It is what occurred with. When KDE, a office for Linux based on gained in popularity, the FSF hastened Trolltech to place Qt under a license (the QPL) which would ensure him always to remain a free software which can be used and developed for regular commercial practices. Thereafter, under the pressure, Trolltech doubled the license of Qt for a use according to the terms of the QPL or the LPG, to improve compatibility with the LPG and to facilitate the diffusion of.
As example, license QPL is also used by LibreSource and OpenVZ.

External bonds

a copy of the license.
objections of the FSF on the QPL
the list of the software licenses of the FSF

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