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Lisence, Opensource to Commercial questions



  • Hello everyone.

    I've been trying to ask Qt Lisence/sales dept about this but I do not think they understand my question.

    When you download Qt from the net you have to select opensource or commercial. And it says somewhere that you cannot mix these or libraries inbetween them. But if I have developed app's with the opensource, then buy Qt commercial, and then rebuild my app in that commercial environment then it will be ok right?

    Also, what happens to the old environment when buying the commercial lisence? will everything change or does Qt/QtCreator store any info about my different environments for a later install?

    Last, I am currently having the opensource lisence on four platforms, will I be able to have this with the commercial lisence or will Qt treat this as using four seats and require that I buy a lisence for all platforms?
    I am using different ip's too on some platforms, though they're never on at the same time I guess Qt might treat this as my lisence being used by others, or will it be ok as it is not being used by two ip's at the same time?


  • Moderators

    @MEMekaniske said in Lisence, Opensource to Commercial questions:

    When you download Qt from the net you have to select opensource or commercial. And it says somewhere that you cannot mix these or libraries inbetween them. But if I have developed app's with the opensource, then buy Qt commercial, and then rebuild my app in that commercial environment then it will be ok right?

    No, you have to have commercial license for the whole duration of the project.

    Also, what happens to the old environment when buying the commercial lisence? will everything change or does Qt/QtCreator store any info about my different environments for a later install?

    I don't think Qt Creator cares for library type it uses to compile. It just runs qmake or cmake.

    Last, I am currently having the opensource lisence on four platforms, will I be able to have this with the commercial lisence or will Qt treat this as using four seats and require that I buy a lisence for all platforms?

    License is for developer, not platform. If you have one developer, you need one license. One developer can work on many platforms (that's the whole point of using Qt! :D). If you have 4 devs, you need 4 licenses.

    I am using different ip's too on some platforms, though they're never on at the same time I guess Qt might treat this as my lisence being used by others, or will it be ok as it is not being used by two ip's at the same time?

    It's ok.

    [Plus the usual disclaimer: I'm not from Qt Company, I'm not a lawyer etc. I answered to my best knowledge but don't treat it as any kind of official advice]


  • Moderators

    @MEMekaniske said in Lisence, Opensource to Commercial questions:

    When you download Qt from the net you have to select opensource or commercial. And it says somewhere that you cannot mix these or libraries inbetween them. But if I have developed app's with the opensource, then buy Qt commercial, and then rebuild my app in that commercial environment then it will be ok right?

    No, you have to have commercial license for the whole duration of the project.

    Also, what happens to the old environment when buying the commercial lisence? will everything change or does Qt/QtCreator store any info about my different environments for a later install?

    I don't think Qt Creator cares for library type it uses to compile. It just runs qmake or cmake.

    Last, I am currently having the opensource lisence on four platforms, will I be able to have this with the commercial lisence or will Qt treat this as using four seats and require that I buy a lisence for all platforms?

    License is for developer, not platform. If you have one developer, you need one license. One developer can work on many platforms (that's the whole point of using Qt! :D). If you have 4 devs, you need 4 licenses.

    I am using different ip's too on some platforms, though they're never on at the same time I guess Qt might treat this as my lisence being used by others, or will it be ok as it is not being used by two ip's at the same time?

    It's ok.

    [Plus the usual disclaimer: I'm not from Qt Company, I'm not a lawyer etc. I answered to my best knowledge but don't treat it as any kind of official advice]



  • There is also the crazy/brain-damaged https://www.qt.io/faq/

    2.13. If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?
    .
    This is not permitted without written consent from The Qt Company. If you have already started the development with an open-source version of Qt, please contact The Qt Company to resolve the issue.

    No idea what they think they are trying to enforce here, but there you are.... You could probably ditch all your work so far and retype it in under commercial licence from memorizing every line ;-)


  • Moderators

    @JonB said in Lisence, Opensource to Commercial questions:

    There is also the crazy/brain-damaged https://www.qt.io/faq/

    2.13. If I have started development of a project using the open source version (LGPL), can I later purchase a commercial version of Qt and move my code under that license?
    .
    This is not permitted without written consent from The Qt Company. If you have already started the development with an open-source version of Qt, please contact The Qt Company to resolve the issue.

    No idea what they think they are trying to enforce here, but there you are....

    Because the license is so outrageously expensive, many companies are developing using LGPL and then only buying the license a few days before product release. This is costing Qt Company serious money so they try to enforce use of commercial license from the very beginning. It does make sense to me.

    Although as far as I understand LGPL and copyright, it is perfectly fine to develop something in-house using LGPL or even GPL - before a product is released, all users are within a single company and do have full access to the source code - so GPL is not breached... but all employees can do whatever they want with that code (even publish it online!).

    All that said, I am pretty sure that if the license had a sane price, this whole problem would simply vanish, people would buy the license upfront and not worry about any legal tricks and quirks.



  • @sierdzio Thanks a lot!

    I think having a lawyer going over Qt's docs costs me a lot more then just buying it.

    I'll take the disclaimer to mind, but seems pretty spot on.

    Thanks again!


  • Moderators

    Good luck!

    Hah, the irony... having to buy a license because it's cheaper than hiring a lawyer to check if buying a license is necessary :D



  • @JonB Thanks for that input! :)
    I'm glad I've only been playing around trying so far, except for a few classes I'll be using as tools in most programs I'll write.

    Probably better just to write it again as you say.. Though it hurts a bit..



  • @sierdzio hehe indeed!


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