3.1. Why is Qt licensed also under an open source license?
We believe in the Free Software movement where using software comes with certain rights, but also certain obligations. Use of open source licensing gives users four primary degrees of freedom when using Qt applications or devices:
The freedom to run the program for any purpose
The freedom to study how the program works and adapt it to specific needs
The freedom to redistribute copies so you can help your neighbor
The freedom to improve the program and release your improvements to the public, so that the whole community benefits
The Free Software community has thrived because of these rules, but there are also developers who never intend to observe these rules, and thus should get a commercial license. The Qt Company exists to support both sets with the dual offering.