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QT LGPL for Commercial



  • Hi Everyone,
    I downloaded qt from official site, and i used the source code to compile .so libraries in linux, can i package the libraries with the software for commercial usage?
    Thanks for any help.



  • @EricXu1990

    You need to go through the license definitions and see if you would infringe one of the requirements.

    AFAIK a typical infrigement for self-compilation would be already when the libraries are static or when you have altered some of Qt's source code.



  • @koahnig Thanks for Reply.
    I can not fully understand the license because it‘s professional for me.

    I know the two points you said above,but i can not confirm the way i use the source code infringed.



  • @EricXu1990
    I am not a lawyer.

    If you compile .so libraries from a proper release and do not make any changes to the Qt source code, and you don't want any of the few "extra" Qt libraries which require GPL (or commercial) licence (like Qt charts), you can use the Open Source commercially.


  • Lifetime Qt Champion

    Hi,

    Then you need to answer these questions:

    • what licence are you using Qt under ? GPL / LGPL / Commercial ?
    • how did you compile Qt ?
    • did you modify Qt ?
    • how are you distributing your application ?

    WARNING: I am not a lawyer. For a definitive answer you shall contact one.



  • I did a quick google for the Qt LGPL license. Currently, Qt seems to have proper instructions which will not bully you into buying a commercial license instead: https://www.qt.io/faq/3.7.-what-are-my-obligations-when-using-qt-under-the-lgpl

    As the link states you have to be careful which modules you use. There are a few modules which are only available under GPL or commercial license. Usually, this should not be a problem.

    If you link dynamically with Qt you only have to make your users aware of their rights (state that your software uses Qt under LGPL v3 and provide the actual text of the LGPL v3) and make the source code of Qt available to them (you don't have to make your own source code available). The latter can be done in two ways: 1) You can make Qt source available in the same way as your software (e.g. if you distribute your software via download, you can host the Qt source at the same location) or 2) make a written offer (valid for at least 3 months IIRC) to everybody who gets your software to request Qt's source code from you.

    If you link statically with Qt you have to provide users with instructions and tools so they can relink with a different Qt version. On desktops this would most often mean you have to distribute your object files (of your own software) with instructions how to link them to Qt.


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