He's probably referring to QT5. If you're a for-profit business and using QT, most likely your software is closed-sourced which requires a commercial license.
I've worked with a team who develops a windows app which still uses QT4. They cannot migrate to QT5 since it requires a commercial license.
I've worked with a team who develops a windows app which still uses QT4. They cannot migrate to QT5 since it requires a commercial license.