The KDevelop Programming Handbook: Licensing

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### 16. Licensing

This section deals with questions that come up in regards to licensing applications that are created with the KDevelop IDE. First, we will have a look at the default behavior, discuss adavantages of licensing your applications under the GPL and finally will cover issues that come up when developing commercial applications.

### 16.1 The GPL License

The KDevelop IDE itself is licensed under the GNU General Public License. This license ensures that any user can copy, modify and redistribute the KDevelop sourcecode package under the terms of this license. The license itself guarantees this as well as the rights of the KDevelop Team members as the authors of this product.

Out of this reason and the dedication to help free software authors developing their products, all KDevelop generated frameworks contain a GPL licensing reference as well as a copy of the license as well. Developers on the other hand can use this license as a base for distributing their product but are in no way bound to do so.

The author, when using the GPL as the license for his product, also takes advantage out of this:

- you can use any existing code also licensed under the GPL and include it into your package (as long as there are no restrictions that interfere to any code-reuse due to the limitations of the used software's licensing),
- your code has a copyright license that protects your rights as the original author,
- the re-use of your code by other authors improve the general development of free applications.

### 16.2 KDE and Qt Licensing Issues

Especially the Qt licensing caused a lot of trouble for the KDE development community until Qt 2.0 which comes with the new QPL license. The Troll Tech company, as the owner and creator of Qt, delivers the Unix version of the library free of charge, but with the restriction that you cannot change the delivered code and redistribute it without an explicit agreement on their side. This was the reason why many free software developers tended to condemn this licensing, as it wasn't absolutely free, especially to do any changes. On the other hand, the Qt library offers a lot of advantages that make it also very attractive for developing commercial applications:

- By buying a commercial license, you can write portable applications for Unix and Windows platforms
- The provided classes and application framework are providing a good solution for easy application design
- You can develop for Unices without being dependend on the GPL licensing when holding a commercial license

The KDE project on the other hand chose the Qt library as a base for developing a desktop environment for Unix systems as well as an extended application framework enhancing the facilities of the capabilities Qt provides. Developers can make use of KDE's advantages by using the provided libraries, distributed as the KDE libraries.

The KDE libraries themselves are distributed under the LGPL, the GNU Library General Public License. What does this mean to application developers ?

#### Non-commercial Development

For non-commercial development, the Qt library is provided free of charge. Your application can make use of the library as far as it does not change the library and the developer delivers his application sourcecode free of charge as well.

The LGPL of the KDE libraries ensures using the KDE libraries as well for non-commercial development. You can make use of the KDE libraries as you like to or your application may require.

#### Commercial Development

For commercial developement, the Troll Tech company offers buying a commercial license. This allows using the Qt library for development purposes as your application or project may require. You can ship your application in any form, as binaries only or by sourcecode, independed of any GPL licensing.

When using the KDE libraries, you have to watch the LGPL license, which explicitely allows commercial development using the library distributed under the LGPL. You just have to watch the rules of the license to know the restrictions that may arise when using the KDE libraries as a base for commercial application development based on KDE.

### 16.3 Your Product License

Hereby, the KDevelop Team, as the authors of the KDevelop Integrated Development Environment, allows you to distribute any application that has been created by and with using the KDevelop IDE under a license of your choice; only depending on licensing terms that arise from the restrictions that are given by the use of code that is placed in libraries the final product uses. These are:

- For Qt applications: The restrictions of the Qt license that apply to the status of your distribution, whether it may be for non-commercial (free) software or commercial purpose.
- For KDE applications: The restrictions of the Qt license according to the status of your distribution plus the restrictions of the LGPL (GNU Library General Public License) as shipped with your copy of the used KDE libraries.
- for all other pre-generated sourcecode you are free to choose the license

Therefore you can change the default licensing as it is included with any KDevelop generated application framework or base application towards your choice, only by watching the restrictions that arise from any library that is linked to your application.

If you have any additional questions about licensing, feel free to ask the KDevelop Team.

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