Switch from LGPL to GPL



  • Hello everyone!
    I hope this post belongs here, I'm still new to the forum structure.

    However, I thought I should ask the community about a problem I have not yet managed to overcome:

    Currently, my QT license is LGPL. I, however, want to be able to use the MQTT module, which is only available under the GPL license.
    That is perfectly fine by me, as I do license most of my code under the GPL licence anyways, and have it publicly available on GitHub.

    However, I found no way of selecting or changing Licenses, even after spending a good 30 minutes going through various sections. I was also never asked what open source license I wanted to use, and I did check the downloads page - it only ambiguously says "Download under (L)GPL", so no luck there.

    I'm at a bit of a loss because my whole project depends on using the MQTT module, and I sincerely hope that someone here knows how to obtain a GPL license.

    Many thanks,
    David


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    The OpenSource version comes with both GPL/LGPL licenses already.



  • @SGaist I'm glad to hear that!
    However, when using both the QT Online installer (i.e. trying a fresh installation) or the QT Maintenance tool, I am not able to install QT for Automation.
    I also can't include the "mqtt" module, which means it is not present on my system.

    If QT comes with both licenses already, my question would then be how to install QT for Automation


  • Lifetime Qt Champion

    IIRC, with the OpenSource version, you have to build the module yourself which is not something hard, a classic qmake, make, make install combo and you should be good to go.



  • @SGaist Building the module would be acceptable, however I can't find the source for it. I checked GitHub as well as the QT Web page.

    The install instructions for QT for Automation refer solely to the QT online installer and selecting the "QT for Automation" module, which is sadly not listed for me.

    I'm already thankful for your help, I just find it a bit unsatisfying that there are only vague or unfitting instructions provided by the QT company themselves.


  • Lifetime Qt Champion

    The official sources repositories are located at http://code.qt.io/.

    The one that interests you is http://code.qt.io/cgit/qt/qtmqtt.git/

    By the way, it’s Qt, QT stands for Apple’s QuickTime which is likely not something that you are currently interested in :)



  • @SGaist Thank you so much for your help!
    That does indeed seem to be the correct source for my needs.
    I'll try to build and install it later, if I have a problem I know where to post a question for it.

    If you can, I would highly recommend editing the MQTT or Qt for Automation page (or maybe the downloads page) to state where one can find GPL-only modules.
    Right now, everything keeps pointing to using the Downloader/Maintenance tool, which doesn't actually work for users of Open Source, and it creates somewhat of a confusing mess ^^'

    And thanks for the name correction, I hadn't noticed it was important.

    EDIT: The compilation worked. Loading the project up in QtCreator, building it, then running make install from the build folder.
    Thanks a lot for explaining this! I don't think I'd have got it running without the help here :)


  • Lifetime Qt Champion

    What page are you referring to ?


  • Moderators

    @Xasin said in Switch from LGPL to GPL:

    If you can, I would highly recommend editing the MQTT or Qt for Automation page (or maybe the downloads page) to state where one can find GPL-only modules.
    Right now, everything keeps pointing to using the Downloader/Maintenance tool, which doesn't actually work for users of Open Source, and it creates somewhat of a confusing mess ^^'

    An edit was made recently to clarify things (it will become visible when the next version of Qt is released): https://codereview.qt-project.org/#/c/231875/

    Is there anything else you think should be added?

    EDIT: The compilation worked. Loading the project up in QtCreator, building it, then running make install from the build folder.

    Great! Happy coding!



  • @JKSH Thanks a lot for the quick response! I like the new documentation version, as it is pretty clear about what OpenSource users should do.
    I personally feel like a hint to the git repos might be helpful too, maybe something like: "Note to Open Source users: Modules available under only the GPL license have to be built from their source, available under code.qt.io"

    However, with the current version, it's fairly easy to find the Qt MQTT GitHub Repository with a search or two, so this is not as much of an issue as before.

    It's very pleasant to see how responsive Qt is regarding these issues, so thanks a lot for your help!


  • Lifetime Qt Champion

    Just be aware that Github is merely a mirror and there are several projects that aims to provide MQTT support to Qt.


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