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Why Qt has 3 Licenses?

  • Hi,

    I am creating my application using Qt for a while & I am nearing its completion. I want to make it open source, but also have commercial interest in it due to the hard work, time, etc put up by me in it. So I find it apt to release my application under 2 licenses - LGPL & Commercial.

    But then I realise Qt is additionally licensed for GPL also. I am unable to understand why is this done?
    Suggestions, Personal opinions are strongly welcome!

  • The GPL and commercial licenses were first, the LGPL license came later.
    Why the GPL still exists, I don't know. It's maybe a rudiment of Qt. It could be also an agrement with the KDE.

    You should know, if Qt. didn't get updates during a special periodic, the project will be licensed under BSD (see wikipedia: . This led to the creation of the KDE Free Qt foundation, which guarantees that Qt would fall under a BSD-style license should no free/open source version of Qt be released during 12 months. )

  • I'm not a license expert, but I remember that I read in some place that a condition to sell Qt by Trolltech to Nokia was that the code must continue with the GNL open source license.

  • On KDE you find the "KDE free Qt foundation terms":http://www.kde.org/community/whatiskde/kdefreeqtfoundation.php and in there :
    The Foundation has a license agreement with Digia and Nokia. This agreement ensures that the Qt will continue to be available under both the LGPL 2.1 and the GPL 3. Should Digia discontinue the development of the Qt Free Edition under these licenses, then the Foundation has the right to release Qt under a BSD-style license or under other open source licenses. The agreement stays valid in case of a buy-out, a merger or bankruptcy.

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