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Using qt for a commercial application on windows (LGPL)

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  • J Offline
    J Offline
    Jo Jo
    wrote on last edited by
    #25

    Sorry, do I need to additionally provide the text of the LGPL license in software or on the some web page?

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    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by SGaist
      #26

      Yes, with the software. Also QMainWindow QApplication has an aboutQt method that shows this information.

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

      J 1 Reply Last reply
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      • SGaistS SGaist

        Yes, with the software. Also QMainWindow QApplication has an aboutQt method that shows this information.

        J Offline
        J Offline
        Jo Jo
        wrote on last edited by Jo Jo
        #27

        @SGaist
        I can't find the QMainWindow::aboutQt method in the documentation. Can you provide a link? I found QApplication::aboutQt but it gives us general information about Qt licensing (not specific to LGPL)

        One more question: can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example

        SGaistS Z 2 Replies Last reply
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        • J Jo Jo

          @SGaist
          I can't find the QMainWindow::aboutQt method in the documentation. Can you provide a link? I found QApplication::aboutQt but it gives us general information about Qt licensing (not specific to LGPL)

          One more question: can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example

          SGaistS Offline
          SGaistS Offline
          SGaist
          Lifetime Qt Champion
          wrote on last edited by
          #28

          @Jo-Jo My bad it was QApplication::aboutQt

          Interested in AI ? www.idiap.ch
          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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          1
          • J Jo Jo

            @SGaist
            I can't find the QMainWindow::aboutQt method in the documentation. Can you provide a link? I found QApplication::aboutQt but it gives us general information about Qt licensing (not specific to LGPL)

            One more question: can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example

            Z Offline
            Z Offline
            zvoopz
            wrote on last edited by zvoopz
            #29

            @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

            can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example

            I dont know which type of license does Viber use. I cant find any information about licenses inside this application but I see a bunch of Qt`s dlls here
            C:\Users\username\AppData\Local\Viber
            No Qt mention as well
            image.PNG

            J 1 Reply Last reply
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            • Z zvoopz

              @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

              can anyone provide me with a link to a commercial Windows application that uses Qt under the LGPL license? I need such a program as an example

              I dont know which type of license does Viber use. I cant find any information about licenses inside this application but I see a bunch of Qt`s dlls here
              C:\Users\username\AppData\Local\Viber
              No Qt mention as well
              image.PNG

              J Offline
              J Offline
              Jo Jo
              wrote on last edited by
              #30

              @zvoopz said in Using qt for a commercial application on windows (LGPL):

              No Qt mention as well

              Probably they are using commercial license but I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)

              Pl45m4P 1 Reply Last reply
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              • J Jo Jo

                @zvoopz said in Using qt for a commercial application on windows (LGPL):

                No Qt mention as well

                Probably they are using commercial license but I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)

                Pl45m4P Offline
                Pl45m4P Offline
                Pl45m4
                wrote on last edited by Pl45m4
                #31

                @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

                I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)

                I think it might be hard to tell, because to know this, you have to get the source code, which commercial app developers would not publish.
                And AFAIK commercial Qt users can link Qt statically while keeping the code hidden. So as "customer" you are not able to tell whether such app even uses Qt.
                Meanwhile, commercial LGPL developed apps you also have to buy first to inspect the files that are shipped with it.
                (I don't have any apps I paid for, that were developed using Qt)

                You could check the Windows App Store. Maybe there you find apps tagged with "Qt" (if there is such feature).
                Or look into the Showcase subforum here. Maybe you find links to commercial apps that were developed by open source users here in the forum.


                If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                ~E. W. Dijkstra

                J 1 Reply Last reply
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                • Pl45m4P Pl45m4

                  @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

                  I am interested in example of app which releases under LGPL (no payment for Qt license, but commercial app)

                  I think it might be hard to tell, because to know this, you have to get the source code, which commercial app developers would not publish.
                  And AFAIK commercial Qt users can link Qt statically while keeping the code hidden. So as "customer" you are not able to tell whether such app even uses Qt.
                  Meanwhile, commercial LGPL developed apps you also have to buy first to inspect the files that are shipped with it.
                  (I don't have any apps I paid for, that were developed using Qt)

                  You could check the Windows App Store. Maybe there you find apps tagged with "Qt" (if there is such feature).
                  Or look into the Showcase subforum here. Maybe you find links to commercial apps that were developed by open source users here in the forum.

                  J Offline
                  J Offline
                  Jo Jo
                  wrote on last edited by
                  #32

                  @Pl45m4 ok, thank you!

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                  • S Offline
                    S Offline
                    SimonSchroeder
                    wrote on last edited by
                    #33

                    BTW, any app needs to comply with the same rules when using Qt under the GPL or LGPL. It doesn't matter if it's commercial or not. As soon as you distribute a binary (even if it is open source) you need to follow these rules. So, open source apps using Qt will suffice as example. Just note that just because someone else isn't doing something (e.g. not providing a download link for the Qt sources) doesn't mean this is the correct way to do it.

                    jsulmJ 1 Reply Last reply
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                    • S SimonSchroeder

                      BTW, any app needs to comply with the same rules when using Qt under the GPL or LGPL. It doesn't matter if it's commercial or not. As soon as you distribute a binary (even if it is open source) you need to follow these rules. So, open source apps using Qt will suffice as example. Just note that just because someone else isn't doing something (e.g. not providing a download link for the Qt sources) doesn't mean this is the correct way to do it.

                      jsulmJ Offline
                      jsulmJ Offline
                      jsulm
                      Lifetime Qt Champion
                      wrote on last edited by
                      #34

                      @SimonSchroeder said in Using qt for a commercial application on windows (LGPL):

                      It doesn't matter if it's commercial or not

                      I disagree with this statement. As far as I know as commercial user you do not have to follow GPL/LPLG as you get Qt under commercial license, not GPL/LGPL (dual licensing).

                      https://forum.qt.io/topic/113070/qt-code-of-conduct

                      SGaistS 1 Reply Last reply
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                      • jsulmJ jsulm

                        @SimonSchroeder said in Using qt for a commercial application on windows (LGPL):

                        It doesn't matter if it's commercial or not

                        I disagree with this statement. As far as I know as commercial user you do not have to follow GPL/LPLG as you get Qt under commercial license, not GPL/LGPL (dual licensing).

                        SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #35

                        @jsulm said in Using qt for a commercial application on windows (LGPL):

                        @SimonSchroeder said in Using qt for a commercial application on windows (LGPL):

                        It doesn't matter if it's commercial or not

                        I disagree with this statement. As far as I know as commercial user you do not have to follow GPL/LPLG as you get Qt under commercial license, not GPL/LGPL (dual licensing).

                        I think @SimonSchroeder meant that when using Qt under GPL/LGPL, the fact that the application is commercial or open source does not change anything with regard to respecting these licenses constraints.

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                        • J Offline
                          J Offline
                          Jo Jo
                          wrote on last edited by
                          #36

                          So, guys, what should I do then? We don't have an example on hand that would prove that all these messages in this topic work effectively in practice. I'm tormented by the question: what if it turns out that following all these rules is not enough to use qt for free? After all, we don't have real examples of anyone who did this and didn't have any problems

                          Pl45m4P S 2 Replies Last reply
                          0
                          • J Jo Jo

                            So, guys, what should I do then? We don't have an example on hand that would prove that all these messages in this topic work effectively in practice. I'm tormented by the question: what if it turns out that following all these rules is not enough to use qt for free? After all, we don't have real examples of anyone who did this and didn't have any problems

                            Pl45m4P Offline
                            Pl45m4P Offline
                            Pl45m4
                            wrote on last edited by
                            #37

                            @Jo-Jo

                            That's because we aren't lawyers and why you may consult one if you want to be 100% safe.


                            If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                            ~E. W. Dijkstra

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                            • SGaistS Offline
                              SGaistS Offline
                              SGaist
                              Lifetime Qt Champion
                              wrote on last edited by
                              #38

                              @Jo-Jo While not using Qt (AFAIK), the firmware from the Garmin GPS uses multiple open source libraries that are listed alongside their licenses for example.

                              Interested in AI ? www.idiap.ch
                              Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                              1 Reply Last reply
                              0
                              • J Jo Jo

                                So, guys, what should I do then? We don't have an example on hand that would prove that all these messages in this topic work effectively in practice. I'm tormented by the question: what if it turns out that following all these rules is not enough to use qt for free? After all, we don't have real examples of anyone who did this and didn't have any problems

                                S Offline
                                S Offline
                                SimonSchroeder
                                wrote on last edited by
                                #39

                                @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

                                After all, we don't have real examples of anyone who did this and didn't have any problems

                                I think we don't have any real example where someone did have problems. It is quite rare that companies get sued over open source licenses. Most of the time it is because they are trying to hide that they are using open source components because they don't want to comply with open source licenses (e.g. tivoization). It is also mostly large companies that get sued because they don't think they have to follow the rules. I don't think you'll get sued if you are trying your best to fulfill open source licenses (though legally speaking "doing your best" is not enough). The major problem in correctly answering your question is that there is no legal precedent how to comply with the LGPL. If you ask Qt they will always tell you that they don't know (it's because there is no legal precedent) and they'll offer you a commercial license to be on the safe side.

                                I'd always choose the LGPL (even for a commercial application). The way I am using Qt I don't see any advantage in a commercial license. The only good thing about the commercial license is peace of mind. But, it is a little expensive for that (especially if you have multiple developers on the project; even more so, if some developers just occasionally program a small part of the software like two weeks a year).

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                                • J Offline
                                  J Offline
                                  Jo Jo
                                  wrote on last edited by Jo Jo
                                  #40

                                  After all the messages, unfortunately, I still couldn't get a concrete answer about whether it is possible to use Qt for Windows app with the LGPL license for free and safely or not. Only at your own risk or buy a license.

                                  Pl45m4P 1 Reply Last reply
                                  0
                                  • J Jo Jo

                                    After all the messages, unfortunately, I still couldn't get a concrete answer about whether it is possible to use Qt for Windows app with the LGPL license for free and safely or not. Only at your own risk or buy a license.

                                    Pl45m4P Offline
                                    Pl45m4P Offline
                                    Pl45m4
                                    wrote on last edited by Pl45m4
                                    #41

                                    @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

                                    whether it is possible to use Qt for Windows app with the LGPL license for free and safely or not

                                    100% you can. But you have to follow some rules/comply with the obligations. Everything that was said above.
                                    Still: None of us is a lawyer. Most people speak from their personal experience.

                                    Only at your own risk

                                    Almost everything you do (on- and offline) is at your own risk :)
                                    If you mess up, no one else is responsible for it but yourself. You can't blame people here in the forum for that :)
                                    That's why it's tricky to ask for legal advices here.


                                    If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                                    ~E. W. Dijkstra

                                    J 1 Reply Last reply
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                                    • Pl45m4P Pl45m4

                                      @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

                                      whether it is possible to use Qt for Windows app with the LGPL license for free and safely or not

                                      100% you can. But you have to follow some rules/comply with the obligations. Everything that was said above.
                                      Still: None of us is a lawyer. Most people speak from their personal experience.

                                      Only at your own risk

                                      Almost everything you do (on- and offline) is at your own risk :)
                                      If you mess up, no one else is responsible for it but yourself. You can't blame people here in the forum for that :)
                                      That's why it's tricky to ask for legal advices here.

                                      J Offline
                                      J Offline
                                      Jo Jo
                                      wrote on last edited by Jo Jo
                                      #42

                                      @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                      100% you can

                                      @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                      is at your own risk

                                      @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                      Most people speak from their personal experience.

                                      Very interesting :)) Anyway, nobody in this topic can provide some successfully example of LGPL qt usage under Windows

                                      Pl45m4P SGaistS 2 Replies Last reply
                                      0
                                      • J Jo Jo

                                        @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                        100% you can

                                        @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                        is at your own risk

                                        @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                        Most people speak from their personal experience.

                                        Very interesting :)) Anyway, nobody in this topic can provide some successfully example of LGPL qt usage under Windows

                                        Pl45m4P Offline
                                        Pl45m4P Offline
                                        Pl45m4
                                        wrote on last edited by Pl45m4
                                        #43

                                        @Jo-Jo said in Using qt for a commercial application on windows (LGPL):

                                        Very interesting :)) Anyway, nobody in this topic can provide some successfully example of LGPL qt usage under Windows

                                        @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                        Almost everything you do (on- and offline) is at your own risk :)
                                        If you mess up, no one else is responsible for it but yourself. You can't blame people here in the forum for that :)

                                        Consult a laywer if you want to be 100% sure.
                                        What I meant above is that what you are planning to do is possible in general, but there are some restrictions and obligations that come with it...
                                        whether you choose to follow them or not is up to you :)

                                        Nobody will give you legal advices here in the forum. Nobody else is responsible for your license.
                                        What you need to do depends on your actual case... the "frame" (what you must and can do) was provided in detailed answers by @SimonSchroeder , @IgKh, @jsulm, @KH-219Design and @SGaist


                                        If debugging is the process of removing software bugs, then programming must be the process of putting them in.

                                        ~E. W. Dijkstra

                                        J 1 Reply Last reply
                                        1
                                        • J Jo Jo

                                          @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                          100% you can

                                          @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                          is at your own risk

                                          @Pl45m4 said in Using qt for a commercial application on windows (LGPL):

                                          Most people speak from their personal experience.

                                          Very interesting :)) Anyway, nobody in this topic can provide some successfully example of LGPL qt usage under Windows

                                          SGaistS Offline
                                          SGaistS Offline
                                          SGaist
                                          Lifetime Qt Champion
                                          wrote on last edited by
                                          #44

                                          @Jo-Jo under Windows ? Krita for example. There's a whole lot of KDE based software that are available on Windows.

                                          Interested in AI ? www.idiap.ch
                                          Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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