I have seen that QT framework offers 4 licenses, as shown here: https://www.qt.io/product/features
Commercial: A commercial license keeps your code proprietary where only you can control and monetize your end product’s development, user experience and distribution – securing your intellectual property.
As I understand it, the commercial license gives you complete freedom on what to do with QT. But it is also an overkill for small applications and individual developers, because:
The Qt Small Business license has all the Qt features for mobile, desktop, and embedded development for 499 USD per year.
This leads me to a question: What would happen if I were to buy this license, develop an application, but only pay the license for the time of the development of the application? Would the application need to change to an open-source license after I stop paying the annual fee?
As an alternative to the commercial license, we have the LGPLv3, GPLv2 and GPLv3 licenses.
TL;DR, from what I currently understand, the LGPLv3 license also lets us do what we want, with the following limitations:
- Must dynamically link to QT libraries
- Cannot use the grayed out features/libraries.
The second limitation I don't understand very well, because design tools are grayed out as well, does this mean I cannot use them, or that I cannot include the actual design tools in my application?
And finally the GPLv2/3 license. From what I understand, I can use most features, but my application needs to be open source and under that same license. Is this correct?