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The same old topic: Licensing.

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  • E Offline
    E Offline
    esdrasbeleza
    wrote on last edited by
    #1

    Hi,

    I need to prepare a lecture for my colleagues about Qt Development, and one of the topics is licensing. But it's a very controversial topic, since the three Qt licenses make its licensing hard to understand. I tried to read "Qt Licensing(Qt Licensing)":http://qt.nokia.com/products/licensing) a few times, but I'm still confused.

    So, I'll start with a some questions:

    1. Can I develop and deploy closed-sourced commercial applications without buying a commercial license of Qt?

    2. A more specific question, since the answer may be different: can I develop and deploy closed-sourced commercial applications without buying a commercial license of Qt, distributing it with the original Qt libraries, without any changes on it?

    My personal projects are free and open sourced, but I need these questions answered so I could convince (or not...) some coworkers to use Qt on their commercial projects.

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    • A Offline
      A Offline
      aavit
      wrote on last edited by
      #2

      IANAL, but in my understanding: Yes & yes. You need to comply with the LGPL 2.1 though.

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        ucomesdag
        wrote on last edited by
        #3

        To my understanding you must also make the source code available.

        Write “Qt”, not “QT” (QuickTime).

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        • E Offline
          E Offline
          esdrasbeleza
          wrote on last edited by
          #4

          [quote author="ucomesdag" date="1275403434"]To my understanding you must also make the source code available.[/quote]

          Which source code?

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          • D Offline
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            DenisKormalev
            wrote on last edited by
            #5

            Not a lawyer too, but AFAIK you can distribute your closed-source commercial software with or without original Qt libraries if you use LGPL. And you con't need to provide source code by this license.
            AFAIR there are some issues with static linking with Qt libraries.

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              aavit
              wrote on last edited by
              #6

              You do not need to distribute the application source code (ref. LGPL section 6) as long as the application is only dynamically linked to Qt (which is the ordinary case). Then the LGPL allows you to distribute your application under "the terms of your choice" (i.e. any license you like), provided that those terms "permit modification of the work [i.e., your application] for the customer's on use and reverse engineering for debugging such modifications."

              If you modify Qt itself, then you must distribute the source code of your modified version of Qt if you want to distribute an application that uses it. You still do not have to distribute the source code of your application.

              (Standard disclaimer: this is not official Nokia legal advice blah blah blah)

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              • J Offline
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                jorj
                wrote on last edited by
                #7

                [quote author="aavit" date="1275465885"]"permit modification of the work [i.e., your application] for the customer's on use and reverse engineering for debugging such modifications."[/quote]

                To what extent is this required, do you just not sue them when they hack your app, or provide the ability to write plugins, or prpovide debug libraries (basically as good as source code, isn't it?)

                This is very interesting, I love Qt personally... But I always thought the licencing thing would stop me producing closed source apps or commercial programs...

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                • A Offline
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                  aavit
                  wrote on last edited by
                  #8

                  [quote author="jorjpimm" date="1275466723"] To what extent is this required, do you just not sue them when they hack your app, or provide the ability to write plugins, or prpovide debug libraries (basically as good as source code, isn't it?)[/quote]

                  As I read it, the LGPL in this regard only places restrictions on the terms of the (optionally commercial, closed-source) license that you choose to distribute your application under. In effect, the LGPL says that that license may not contain things like "modifications or reverse-engineering is not allowed".

                  The FSF may provide more in-depth on this: http://www.fsf.org/licensing/

                  [quote author="jorjpimm" date="1275466723"] This is very interesting, I love Qt personally... But I always thought the licencing thing would stop me producing closed source apps or commercial programs...[/quote]

                  While that might have been an issue earlier, while Qt was under Trolltech's business model, it should not be now, after Nokia started releasing Qt under LGPL also (which happened about a year ago).

                  (Standard disclaimer applies)

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                  • J Offline
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                    jorj
                    wrote on last edited by
                    #9

                    more open than i thought! Cool, however open source will still remain my distribution of choice i think.

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                    • M Offline
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                      mgran
                      wrote on last edited by
                      #10

                      Have a look at this blog post for information about this directly from Qt legal:

                      "http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/(http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/)":http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/

                      Project Manager - Qt Development Frameworks

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                      • J Offline
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                        jorj
                        wrote on last edited by
                        #11

                        [quote author="MariusG" date="1275501216"]Have a look at this blog post for information about this directly from Qt legal:

                        "http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/(http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/)":http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
                        [/quote]

                        Has that page changed recently? Because I'm sure I have been on a page with the same title, and it used to be not so useful, but now looks very good.

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                        • M Offline
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                          mgran
                          wrote on last edited by
                          #12

                          Apart from a small css update it's the same as before.

                          Project Manager - Qt Development Frameworks

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                          • U Offline
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                            ucomesdag
                            wrote on last edited by
                            #13

                            [quote author="MariusG" date="1275501216"]Have a look at this blog post for information about this directly from Qt legal:

                            "http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/(http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/)":http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/
                            [/quote]

                            Thanks that made it all clear to me!

                            Write “Qt”, not “QT” (QuickTime).

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                            • S Offline
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                              sfilippidis
                              wrote on last edited by
                              #14

                              Since comments at

                              http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/

                              are closed, I was wondering if I could have an answer at the following scenario/question:

                              If someone writes a closed-source Qt application for Windows based on the LGPL-licenced Qt framework, and if he/she doesn't change the libraries, and if he/she linked dynamically with the dlls (Qt for Windows) then:

                              a) if he/she doesn't provide the dlls but he/she only provides the exe
                              b) if he/she provides both the exe and the dlls

                              does he/she has to provide the (unchanged) source code of the dlls?

                              https://www.filippidis.name/

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                                DenisKormalev
                                wrote on last edited by
                                #15

                                Stavros Filippidis, AFAIK in both cases you shouldn't provide code.

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                                  sfilippidis
                                  wrote on last edited by
                                  #16

                                  @_Denis Kormalev_: Just to clarify, I am NOT referring to the source code of the application, but to the source code of the Qt libraries (QtCore4.dll, QtGui4.dll, etc). In any case, I am not a lawyer, I am just have these questioned unanswered. :)

                                  https://www.filippidis.name/

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                                  • D Offline
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                                    DenisKormalev
                                    wrote on last edited by
                                    #17

                                    [quote author="Stavros Filippidis" date="1276707919"]@_Denis Kormalev_: Just to clarify, I am NOT referring to the source code of the application, but to the source code of the Qt libraries (QtCore4.dll, QtGui4.dll, etc). In any case, I am not a lawyer, I am just have these questioned unanswered. :)[/quote]

                                    Yeah, I understood that question is about Qt sources. Anyway when you use Qt with LGPL license you need to provide link to Qt. And everybody who wants can take sources from Qt website.

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                                    • J Offline
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                                      jorj
                                      wrote on last edited by
                                      #18

                                      (oooh, second page, ive never seen that before, very cool)

                                      I think Qt could do more to explain its licences simply, as the previously linked page tried to do... I think there could be a further simplification of it...

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                                      • T Offline
                                        T Offline
                                        troubalex
                                        wrote on last edited by
                                        #19

                                        We agree. However, licensing (and law in general) unfortunately isn't easy to simplify while giving correct information...

                                        THE CAKE IS A LIE
                                        Web Community Manager - Qt Development Frameworks

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                                        • S Offline
                                          S Offline
                                          sfilippidis
                                          wrote on last edited by
                                          #20

                                          @Alexandra: In my opinion, it would be interesting if you would consider re-opening comments at

                                          http://blog.qt.nokia.com/2009/11/30/qt-making-the-right-licensing-decision/

                                          so that someone from Qt/Nokia's legal department could clarify additional questions that we could post there. ;)

                                          https://www.filippidis.name/

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