@JohannesW said in Mix commercial and open source:
Or are you not allowed to mix things under any circumstances, even if it only affects the development?
You are not allowed to mix code that was developed with Qt commercial license(s) and such that was developed with Qt's LGPL offering. TQtC's concern being that you can develop a whole system with LGPL and then decide that you want to jump to commercial to close the source completely (i.e. to decide you don't want oblige the requirements of the LGPL at some point after the code is already developed).
In any case you can use the LGPL to develop commercial software, simply don't mix the licenses.