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I am a new user of Qt...I want to know can I create commercial and closed source applications using Qt4(LGPL Licensed)? and also what is the difference between Qt4(LGPL version) and Qt4(Commercial version)?

Thanks in advance...

Bala Krish
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    Did you even search for anything? See [this](http://stackoverflow.com/q/139251/594137), [this](http://stackoverflow.com/q/453954/594137), [this](http://stackoverflow.com/q/1067884/594137), [this](http://stackoverflow.com/q/1356918/594137), and [this](http://stackoverflow.com/q/1372396/594137). – Samuel Harmer Jan 06 '12 at 15:30
  • Found [another](http://stackoverflow.com/q/94346/594137) – Samuel Harmer Jan 06 '12 at 15:39

4 Answers4

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The LGPL allows for use in proprietary products. One thing you do have to do when using an LGPL library is allow the end-user to replace the library code with their own (modified) equivalent, implying dynamic linking to your actual application in most cases.

That's why the commercial edition of Qt touts static linking as one of its features, on top of the other features relating to development support.

slyfox
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LGPL licensing means that you can use Qt in your application, link to it (this part is a bit confused, but it is specifically allowed for Qt thanks to a special exception), and not have to license your application as open source. The Qt library itself, however, is still open source, and you're not allowed to publish new version of Qt without providing the source code.

GPL licensing means that you can't use it at all on closed source applications (well, you can use it, but you can't publish it).

The Commercial licensing is if you want to make changes to Qt and not publish them. For example, you would need the commercial licensing if you wanted to develop a new version of Qt for your mobile phone platform, and wanted to keep parts of it as closed source. This licensing option isn't very interesting to application programmers.

cha0site
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Yes, the LGPL does allow commercial/closed source applications. That's the main difference between GPL and LGPL.

From what I can tell, the Qt commercial is basically for commercial "support" for the product, and in case the LGPL license doesn't suit your needs.

Eve Freeman
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As you can see on the QT website:

We license Qt under the terms of the GNU Lesser General Public License (LGPL) version 2.1.

This version of Qt is appropriate for the development of Qt applications (proprietary or open source) provided you can comply with the terms and conditions contained in the GNU LGPL version 2.1.

Additionally, we have reached an agreement with Digia, who provides Qt under the terms of a commercial licensing agreement. This version of Qt is called Qt Commercial. To find out more about Qt Commercial, please visit qt.digia.com.

They also say that, usually, the LGPL version is OK for Symbian, Maemo or MeeGo development.

The LGPL basically allows commercial/closed-source software.

So take a look at the LGPL, to check if it's ok for you. if not, you'll have to use the commercial license.

Macmade
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