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[Solved] Releasing a software built using Qt?

  • Hi,
    I would like to know what all standard steps must be followed for releasing a software built using Qt by dynamic linking?
    To be specific I am concerned about the license files I need to re-distribute.
    Currently I am re-distributing lgpl 2.1.txt along with my application.
    Additionally I have provided the About Qt button in the About dialog of my application.
    Is there something more that I am missing?
    I am using Qt 5.2.1.

  • Moderators

    I think you are fine. One thing you could add the lgpl-exception.txt, as it is also needed.

  • Hi sierdzio,

    Thank You for your answer.
    Can you please tell me where I can find this lgpl-exception.txt?
    Is this Qt specific or published by GNU?

  • Moderators

    It is distributed with every copy of Qt. It is Qt-specific. Here is a link to a copy from Qt documentation: "link":

  • I am having trouble understanding what it states.
    I am obviously including Qt header files like:

    @#include <QMessageBox>@

    Does the line may incorporate material from a header file refer to this?
    Or does it refer to copying code from header files without including them?

    Anyways it seems to me like an instruction for developers.
    Should I re-distribute this notice with my software as well?

  • Moderators

    OK, that is one of 2 wordings this exception has... another exception can be found in the same folder Qt has LGPL text. I have raised the issue with Qt developers a few months ago. The response was a bit strange, as if they did not care much.

    About the meaning of this exception (the other has another meaning :/ ): I am not sure, but it talks about object code. So this is about the results that are produced by the compiler, apparently. When it compiles the code, it will inject some of the stuff from Qt headers into your code (inline functions, for example). So I think it is just another legal way of saying: we give you more rights than LGPL does. ;-)

    I do not know whether you need to distribute that file with your application. You definitely can, but I don't see any obligation to do so anywhere.

  • Moderators

    Just for reference, here is the other wording I have been talking about (taken from Qt 5.3.0 source code, file named LGPL_EXCEPTION.txt):
    [quote]Digia Qt LGPL Exception version 1.1

    As an additional permission to the GNU Lesser General Public License version
    2.1, the object code form of a "work that uses the Library" may incorporate
    material from a header file that is part of the Library. You may distribute
    such object code under terms of your choice, provided that:
    (i) the header files of the Library have not been modified; and
    (ii) the incorporated material is limited to numerical parameters, data
    structure layouts, accessors, macros, inline functions and
    templates; and
    (iii) you comply with the terms of Section 6 of the GNU Lesser General
    Public License version 2.1.

    Moreover, you may apply this exception to a modified version of the Library,
    provided that such modification does not involve copying material from the
    Library into the modified Library's header files unless such material is
    limited to (i) numerical parameters; (ii) data structure layouts;
    (iii) accessors; and (iv) small macros, templates and inline functions of
    five lines or less in length.

    Furthermore, you are not required to apply this additional permission to a
    modified version of the Library.[/quote]

  • Yeah seems a bit convoluted.
    Thanks for explaination!
    I guess I will re-distribute it just for the sake of it.
    Apart from that I think ThirdPartySoftware_Listing.txt should also be re-distributed...

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