[PyQt] License for embedded PyQt in Qt C++ app

Matt Newell newellm at blur.com
Fri Dec 18 18:26:31 GMT 2009

> If you are not using PyQt you can release your application under LGPL.
> Sip license seems to allow that if I have properly understood it:
> http://www.riverbankcomputing.co.uk/software/sip/license
> If I have misunderstood it the rest of my mail will be senseless.
> At the moment you or your partners start programming using PyQt,
> you/they are bound to the GPL license. If you are distributing the
> source code and not charging anything, it should not make a difference
> to you. If your partners do not want to distribute their modified codes
> it does not make any difference to them either. So, you could clearly
> state it when distributing your code and say that if they use PyQt they
> are bound to the GPL license whenever they distribute derived work and
> that the only way to overcome that "problem" is to acquire a license
> from Riverbank.
> Armando

I'm pretty sure the c++ part of the application can be released under the LGPL 
or any license considered compatible with the GPL, so long as it doesn't 
depend on the pyqt modules built on top.  Any code derived from pyqt, 
directly or indirectly, would need to be licensed under the GPL, or developed 
with a commercial pyqt license.

To illustrate, if the application is split into 3 components:
A - The c++ part, which can be built and used without linking to sip or pyqt
B - The custom sip modules, which require both sip and pyqt
C - The application python scripts, which are derivative of A and B.

Both "B" and "C" must be released under the terms of the GPL unless you buy a 
commercial pyqt license.  "A" can be released under ANY license that is GPL 
compatible, such as the LGPL.

Here's a chart of license compatibility.


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