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Re: QT non-free but becoming compatible to debian? (was Re: Qt license change)

Navindra Umanee <navindra@cs.mcgill.ca> wrote:
> I'm sorry, yes I think I did screw up completely here.  Would you mind
> re-explaining what is wrong with linking a GPL'ed program against a
> QPL library again?  QPL allows you to write a GPL program linked
> against it, so what is the GPL'ed program's problem with the QPL
> library?

The QPL places a restriction on distribution which isn't present in
the GPL.  The GPL grants no permission to distribute the work under
these circumstances.

Oh, and it's not just "linking".  You can't take an arbitrary GPLed
program (let's take gcc as an example of an arbitrary GPLed program)
and just link it against Qt.  You have to modify the program so that
you can "just link" it against Qt.

> I'm seeing:
> -------------
> The source code for a work means the preferred form of the work for
> making modifications to it.  For an executable work, complete source
> code means all the source code for all modules it contains, plus any
> associated interface definition files, plus the scripts used to
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> control compilation and installation of the executable.
> -------------
> So, the interface definition files of Qt would have to be under the
> GPL?  Again, I'm probably screwing up completely.

The GPL requires that the work as a whole -- which includes Qt if we're
discussing an arbitrary kde app -- be distributable under the terms of
the GPL.

The terms of the GPL include:

(1) That modified sources be distributed.
(2) That anyone can further modify those sources and redistribute them
(3) That no special conditions can apply to anyone excercising these rights
[beyond those already present in the GPL].

The QPL limits these rights, so if it's a part of a work which contains
GPLed code, then the GPL grants no distribution rights.


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