Using Qt offline installer for deployment



  • Hi together,

    First some Background:
    I'm using Qt under LGPL for a Windows Desktop application (as dll). So now two main obligations are:

    • Complete corresponding source code of the QtToolkit has to be delivered / shipped.
    • The user needs to be able to recompile, relink and run the re-linked library (sufficient installation information must be provided).

    For me, the easiest way to fullfill these obligations, would be using the Qt offline installer (Available further down here: http://www.qt.io/download-open-source/#section-2 ). If i shipped this installer with my installation or hosted it on my own server, I would fullfill the LGPL (source code and compiler included, I could add a small instruction for the end user). And I would also not depend on Qt servers, because its an offline installer (as Qt explicitly stated: " a link to the source code provided by the Qt Project or Qt Company is not sufficient".)

    Now my question:
    QtToolkit is available under LGPL, so I'm allowed (and obliged) to rehost the code. But what's about the Qt offline installer? I could not find any information on the licence of the whole installer-package. Which licence does the installer have? Am I allowed to rehost / ship the Qt offline installer accompanying my commercial product?

    Thanks in advance!


  • Moderators

    @Digits said in Using Qt offline installer for deployment:

    Complete corresponding source code of the QtToolkit has to be delivered / shipped.
    The user needs to be able to recompile, relink and run the re-linked library (sufficient installation information must be provided).

    actually you only have to publish the changes in the Qt code (if you have made any).
    This enables the user to substitute your shipped Qt dlls with his own compiled Qt libraries. And this is mainly all you have to fulfill to conform LGPL.

    But of course i am not a lawer or anything.



  • @raven-worx said in Using Qt offline installer for deployment:

    actually you only have to publish the changes in the Qt code (if you have made any).
    This enables the user to substitute your shipped Qt dlls with his own compiled Qt libraries. And this is mainly all you have to fulfill to conform LGPL.

    Sorry, but your reply does not answer any of my questions regarding the installer.

    Besides I think your statement is in conflict with the official statements from Qt homepage where Qt states:

    Complete corresponding source code of the library used with the application or the device built using LGPL, including all modifications to the library, should be delivered with the application (or alternatively provide a written offer with instructions on how to get the source code). It should be noted that the complete corresponding source code has to be delivered even if the library has not been modified at all.
    https://www.qt.io/qt-licensing-terms/

    and

    You will need to deliver the complete source code of Qt (including all modifications you did or applied) to your users/customers. Alternatively you need to provide a written offer with instructions on how to get the source code. Please also note that this has to be under your control, so a link to the source code provided by the Qt Project or Qt Company is not sufficient.
    https://www.qt.io/faq/#_Toc_3_7

    I know about the LGPL debate, but I'm not a lawyer either. So better save then sorry - just provide the whole source. But again this topic does not have to be discussed here, my original question was regarding the licence and redeploy of the installer...


  • Moderators

    @Digits "or alternatively provide a written offer with instructions on how to get the source code" - should be enough to provide instructions. I never saw any opensource project using LGPL libraries providing the source code for that libraries.
    In any case this forum is not the correct place to ask such questions as most (all?) of us are not lawyers.


  • Moderators

    @Digits said in Using Qt offline installer for deployment:

    Now my question:
    QtToolkit is available under LGPL, so I'm allowed (and obliged) to rehost the code. But what's about the Qt offline installer? I could not find any information on the licence of the whole installer-package. Which licence does the installer have? Am I allowed to rehost / ship the Qt offline installer accompanying my commercial product?

    (The usual lawyer disclaimers apply)

    I haven't seen any license applied to the installer itself; I've only seen licenses applied to the individual modules contained within the installer. So, if you're allowed to redistribute every module individually (which you are), then I'd imagine you're allowed to redistribute the installer.

    In any case, the source code of the installer itself is available under LGPL too: https://wiki.qt.io/Qt-Installer-Framework

    NOTE 1: The offline installer contains a few libraries that are GPL-only, not LGPL (e.g. Qt Charts). I'm not sure what implications there are for distributing a package that includes these GPL modules.



  • @JKSH said in Using Qt offline installer for deployment:

    I haven't seen any license applied to the installer itself; I've only seen licenses applied to the individual modules contained within the installer. So, if you're allowed to redistribute every module individually (which you are), then I'd imagine you're allowed to redistribute the installer.

    In any case, the source code of the installer itself is available under LGPL too: https://wiki.qt.io/Qt-Installer-Framework

    NOTE 1: The offline installer contains a few libraries that are GPL-only, not LGPL (e.g. Qt Charts). I'm not sure what implications there are for distributing a package that includes these GPL modules.

    Thanks for your hints and for an answer related to my question ;). I'll probably take a closer look into the Installer-Framework and probably build my own installer, also considering your hints concerning the GPL modules.



  • Just in case this might help anyone:

    Th Qt-Installer-Framework (at least version 3.0.1 which I'm using from https://download.qt.io/official_releases/qt-installer-framework/3.0.1/) is published under GPL with exceptions:

    The Qt Company GPL Exception 1.0

    Exception 1:

    As a special exception you may create a larger work which contains the
    output of this application and distribute that work under terms of your
    choice, so long as the work is not otherwise derived from or based on
    this application and so long as the work does not in itself generate
    output that contains the output from this application in its original
    or modified form.

    Exception 2:

    As a special exception, you have permission to combine this application
    with Plugins licensed under the terms of your choice, to produce an
    executable, and to copy and distribute the resulting executable under
    the terms of your choice. However, the executable must be accompanied
    by a prominent notice offering all users of the executable the entire
    source code to this application, excluding the source code of the
    independent modules, but including any changes you have made to this
    application, under the terms of this license.

    The usual lawyer disclaimers apply, but my understanding is:
    Basically you need QT within the installer application itself and you really want to link it statically, because otherwise the installer would not make any sense at all. Normaly you aren't allowed to do this under GPL, but with the above exception you are. Of course this only applies to the installer executable itself and not to the packaged contents (your application). If you pack an Qt application, you have to ship Qt sources with this application inside the installer.

    See also here.


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