Qt under LGPL

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Nokia, the owner of Qt software and therefore the owner of Qt, has announced that the Qt framework will be released under LGPL in the upcoming 4.5 release.

The announcement is a huge change in the licensing policy regarding Qt: up until this change Qt could be used for Free Software development under the GPL – or for proprietary development under a proprietary license including a fee. This was totally ok for many software developers and projects and it was of course the main income source for Trolltech, the company behind Qt which was bought by Nokia.

It was, however, also a big reason why many developers didn’t choose it: some companies wanted to develop closed source without paying this licence free, and other Free Software projects argued that GPL is not free enough for their taste. These reasons are not valid any more, and with Nokia supporting Qt the question arises how this will influence the software world.

Of course the world won’t change it’s face over night, but Qt had always a strong support, and every company which decided to go cross platform at least had a closer look at Qt. Now, with the new license and also combined with the new IDE Qt there are even more reasons to choose Qt for cross platform software development. And since it is a powerful toolkit anyway it might also happen that more and more Windows developers choose Qt – which would make it easier to ask them t develop for Linux as well – and/or for KDE.

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19 thoughts on “Qt under LGPL

  1. It looks like the official KDE 4.2 release is not going to be Qt 4.5 but there has been no announcement. What is the deal?

    Another thing that interests me is how do KDE components that have been incorporated into Qt work from the development point-of-view. Presumably KDE developers sometimes want to make changes.

  2. maninalift, Qt 4.5 will be out in March, KDE 4.2 will be out in some days, so it can’t be based on Qt 4.5
    However, KDE 4.2 will work with Qt 4.5, so you can update your Qt as soon as its out, and KDE 4.2 will benefit from teh fixes inside Qt 4.5.

  3. It’s a stepback from GPLv3/Commercial model for software freedom in general in the QT ecosystem.

    Now you’ll start seeing many more proprietary software around QT and less incentive for free-software start-ups.

    It’s just sad really

  4. It’s a stepback from GPLv3/Commercial model for software freedom in general in the QT ecosystem.

    Now you’ll start seeing many more proprietary software around QT and less incentive for free-software start-ups.

    It’s just sad really

  5. “Now you’ll start seeing many more proprietary software around QT and less incentive for free-software start-ups.”

    Making Qt LGPL wont change FLOSS ecosystem. It won’t stop FLOSS programers from doing floss development… let’s by realistic

    What it will change is exactly the opposite, it will change prioprietary software.

    Two things will happen:
    1) Qt will by used by many new developers from freeware/sharewere world. It is good for FLOSS because when you are already developing freeware in Qt it is easy to add support for Mac and/or Linux.
    2) Companies which are afraid of GPL but still can do their business will likely drop GTK/other_toolkits in favour of Qt. Becouse Qt is supperior and both have the same licence model now.

  6. last anonymous: I don’t understand you – why more commercial software in QT is bad ?

    Nobody loses – the amount of free software is constant (If somebody don’t want to make program free, nobody can force him, he just write it using other library and keep it commercial).

  7. @anonymous:
    So you think that GTK has been a stepback?

    Do you know that even RMS and the FSF advise the LGPL license for libraries?

    Anyway: Qt 4.5 will still have also the GPLv3 and the Commercial options! LGPL will just be one more option added to the present ones.

  8. The LGPL is actually not a good license for C++ libraries:

    http://gcc.gnu.org/onlinedocs/libstdc++/faq.html#faq.license

    “The LGPL requires that users be able to replace the LGPL code with a modified version; this is trivial if the library in question is a C shared library. But there’s no way to make that work with C++, where much of the library consists of inline functions and templates, which are expanded inside the code that uses the library. So to allow people to replace the library code, someone using the library would have to distribute their own source, rendering the LGPL equivalent to the GPL.”

    I hope Nokia adds an exception similar to http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt01ch01s02.html. Otherwise it would still not be possible to write closed source applications with Qt without acquiring a license.

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