Today a friend called me asking about Qt licensing.
Because this is getting a FAQ I decided to write a post to lighten this topic.
The commercial Qt license includes standard support and access to updates and allows you to develop fully closed source software.
The LGPL carries some restrictions regarding the ability for users to relink libraries and other restrictions that may impose architectural requirements that some organizations might not be comfortable with and allows you to develop closed source software when you link it dynamically to Qt libraries.
Qt is licensed under a commercial and open source license (GNU Lesser General Public License version 2.1).
Open Source Licensing
Qt is licensed under under the GNU General Public License (GPL) (version 3) and the GNU Lesser General Public License (LGPL) (version 2.1).
You can use this edition of Qt to create and distribute software with licenses that are compatible with these free software licenses.
LGPL and GPL are complex licenses that contain many obligations and restrictions you must abide with.
Commercial licensing
Alternatively Qt is also licensed under the commercial License of Qt.
This is the correct license to use for the development of proprietary and/or commercial software with Qt where you need to safeguard your development investment to secure your competitive advantage.
You should develop with a Qt commercial license if you:
- Use, modify and redistribute Qt with no obligation to share your source code
- Access technical support and product updates
- Enjoy greater freedom to license your application as you wish
- Use static linking in your application
- Use the additional functionality provided as the part of commercial license
- Need to incorporate proprietary software for mission-critical applications that prohibits use of open source software
- Need for product warranties & indemnities
- Need to secure that your software cannot be accessed or manipulated by end users
The commercial Qt license includes standard support and access to updates and allows you to develop fully closed source software. The LGPL carries some restrictions regarding the ability for users to relink libraries and other restrictions that may impose architectural requirements that some organizations might not be comfortable with.