[SOLVED] Qt SQL Module - Do I have to pay a license for using it ? (commercial use)



  • Hi,

    I was looking for a cross platform C++ API for databases. All of them seems to be NOT free. I saw Qt SQL Module, looks like very interesting but I saw this link that tells it's not free if my app is not open source. Then I checked this Qt licensing link, it's BSD.

    1. So is Qt SQL Module free or not for a [closed source / commercial use] ?
    2. How to know if a Qt Module is free or not ?

    NB: The application is intended to run under Windows or Linux, and may connect to RDBMS like PostgreSQL or other.

    Thanks



  • Hi and welcome to devnet,

    if your application target is desktop platforms (Windows, OS X, Linux) you can user the LGPL version of Qt (so no commercial license needed).

    If you want to use on iOS there some issues and you need to buy a commercial license



  • Thank you for your reply @mcosta,

    Yes my application is intended to run on desktop platforms (Windows or Linux) and I already use Community Edition.

    So does it mean I can freely use classes like QSqlDatabase and QSqlQuery for a [commercial / source closed] application ?

    Thanks,



  • Hi,

    QtSql is available for opensource version. So you can use it for free (is your application si GPL/LGPL compliant)



  • I don't understand what do you mean by "if your application is GPL/LGPL compliant" ?
    This application will only use what Qt has to offer with all its "#include <XXX>".


  • Lifetime Qt Champion

    Hi and welcome to devnet,

    What your application uses from a library and its license are two different things. i.e. if you are using libraries that are GPL only, you can't make your application closed source.



  • Hi,

    in order to user opensource version of Qt you can use GPL or LGPL license.
    If you want to distribute your application, you have to check that the license you'll choose for you application is compatible with the Qt license.

    Ususally if you distribute your application with opensource license (like GPL or LGPL) is not a problem. FOr commercial license you have to care about LGPL expections



  • Hi and thank you for your reply @SGaist,

    Well I am a little bit confused, all I want to do is :
    Creating a desktop application for Windows/Linux with the Qt Framework (including widgets, core, gui and sql modules in my .pro file), using pure C++ development, for a commercial application (which will be source closed at the beginning).

    I don't think I will add another library to my project (maybe Boost, but I know this one is permissive license).

    So am I doing a mistake somewhere ? Thanks


  • Lifetime Qt Champion

    No you don't, again, just check what the LGPL license requires and conform to it, then you'll be good.



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