LGPL License



  • Hello,

    I have read:
    http://www.qt.io/qt-licensing-terms/
    http://qt-project.org/wiki/LicensingQuestions
    http://qt-project.org/search/tag/licensing
    http://www.slideshare.net/qtbynokia/qt-licensing-explained

    I have watch:
    http://www.youtube.com/watch?v=FkAuWvDs8vA

    If I have:

    1. I have my own closed-source application.
    2. My app have proprietary license.
    3. I dynamically link my app with QT libraries
    4. I don't change QT.
    5. I will distribute with my app such libraries as QtCore4.dll, QtGui4.dll, etc. not any source code of QT.
    6. I need to use QT and I choose to use LGPL license for QT in my app.
    7. I don't have enough money to buy commercial license.

    After I have read and watch many docs and resources, I still really don't have a clear answer to next question: will I have any legal problems with QT?



  • I am sure you know that nobody here can give you legal advice, unless they are lawyers doing community work :).

    AFAIK, in addition to what you have listed, you need to distribute Qt's license with your application and make the source code of Qt available from your own website or somewhere (you control/make accessible) from which users of your software can download it. Search for Thiago Macieira's comments on LGPL for the requirement about providing the sources, he had mentioned that but I don't remember when and where.





  • You're not going to set a precedent by publishing your app. There are loads of (commercial/closed source) applications published based on the LGPLed libraries, you're hardly the first one.

    I find the discussion on who should be the one distributing the sources of Qt a bit academic. It seems that people disagree on what is sufficient for fulfilling the license, but I have never heard of any legal action taken against a user of the Qt libraries under LGPL because of a failure to distribute the sources of Qt. Just to be sure, make sure you have a tarball stored somewhere that you can give anyone that asks for it, but don't count on anyone actually doing that.

    And no, IANAL, and neither is Thaigo by the way.


  • Moderators

    Why did you post an image instead of text?

    [quote]And let they already say something precise and clear about license rules and chosen license type for specific application![/quote]If I'm not mistaken, nobody can do that right now (not even lawyers). We can only do that after an actual court case happens.



  • bq. You’re not going to set a precedent by publishing your app. There are loads of (commercial/closed source) applications published based on the LGPLed libraries, you’re hardly the first one.

    Please give me some examples. I want to know details.

    bq. I find the discussion on who should be the one distributing the sources of Qt a bit academic. It seems that people disagree on what is sufficient for fulfilling the license, but I have never heard of any legal action taken against a user of the Qt libraries under LGPL because of a failure to distribute the sources of Qt. Just to be sure, make sure you have a tarball stored somewhere that you can give anyone that asks for it, but don’t count on anyone actually doing that.

    What is sufficient for fulfilling the license?

    bq. LGPL v2.1 (Section 4)
    If distribution of object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place satisfies the requirement to distribute the source code, even though third parties are not compelled to copy the source along with the object code.

    So, provided that I give a link to qt-project.org where source code can be found, it will be quite enough according to terms and conditions of LGPL.
    .
    .
    .
    .

    bq. Why did you post an image instead of text?

    There was a error during posting, I didn't know how to solve it.

    bq. If I’m not mistaken, nobody can do that right now (not even lawyers). We can only do that after an actual court case happens.

    Court!? :) How you are bloodthirsty!
    Even Cristy Hamley said in video "Qt DevDays 2010":
    "...we usually contact the potential violators and have a discussion with them...and are able usually to come to an amicable well resolution, that both parties were happy with.. So I wouldn't say that we have any particularly active enforcement policy, I mean I don't spend my days trolling around on the web looking for the violators license agreements..."

    The main problem is that QT library is very large but the price is the only one! And it's very high!

    For example, I want to use only GUI of QT for my project. I don't need something else. So I will use only 2-3 DLLs from QT library. But the price for commercial license is for QT library at all. Really it's not for one developer or team of 1-3 developers, it's for big companies.

    If QT Company(Digia) would diversify the price, for example one price for GUI, one for Network and so on. It will make commercial license available for one developer or smal team of 1-3 developers.



  • You do realize that there is also the "Indie" option nowadays?

    Anyway: we are using LGPL Qt too, and our software certainly isn't open source. It is very much propriatary. I'm sure there are many others.

    On the providing a link to Qt-projects being enough: that's where opinions differ. Some say it is, some say it isn't. That's why I suggested to make sure you have a tarball available should anyone ask for it.



  • bq. You do realize that there is also the “Indie” option nowadays?

    What is this option? Can you explain more in detail?

    bq. That’s why I suggested to make sure you have a tarball available should anyone ask for it.

    Ok. I must make a tarball of QT sources available for download from my web-site or another my mirror.
    This is the very smart idea of distribution of software under LGPL invented by Richard Matthew Stallman! :)))



  • [quote author="rasjpro" date="1421740839"]bq. You do realize that there is also the “Indie” option nowadays?

    What is this option? Can you explain more in detail?
    [/quote]

    Sorry, that is mobile only I noticed. See the "download page":http://www.qt.io/download/ for details.


  • Moderators

    [quote author="rasjpro" date="1421729557"]
    bq. If I’m not mistaken, nobody can do that right now (not even lawyers). We can only do that after an actual court case happens.

    Court!? :) How you are bloodthirsty!
    Even Cristy Hamley said in video "Qt DevDays 2010":
    "...we usually contact the potential violators and have a discussion with them...and are able usually to come to an amicable well resolution, that both parties were happy with.. So I wouldn't say that we have any particularly active enforcement policy, I mean I don't spend my days trolling around on the web looking for the violators license agreements..." [/quote]Please don't misunderstand me: I'm not saying I want a court case. I'm saying that you should understand the subtle difference between these two questions:

    "What is sufficient for fulfilling the LGPL license?"

    "What is sufficient for fulfilling the Qt Company's requirements for the LGPL version of Qt?"

    Question #1 cannot be fully answered yet, because there have been no court cases*, so there is no legal precedent. Note that, in the future, the answer to Question #1 might even be different in different countries.

    (*Well, there is "this case":http://www.h-online.com/open/news/item/German-court-case-confirms-validity-of-the-LGPL-1822882.html, but the offender didn't even try to fulfil the LGPL at all)


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