is it possible to use the software after the 1 year update period as it is, without updates? Or do I need to buy every year again with 30% off? Answer: QCAD - Accessing Downloads
And how the OpenSourceCommunity profits from this business? Are there any refunds going back to the community?
And where can I see the source code, if neccessary?
Answered: found the github sourcecode.
It is the access to your personal download area that expires after 1 year.
The licence and the copy of QCAD Pro is personal and perpetual.
QCAD Pro includes enhanced proprietary plugins, specialized tools and so on.
QCAD/CAM extends that further with CAM plugins.
Bugs may get fixed in the open source part of QCAD or basic tools may get updated.
Required functionality may be added.
In this way QCAD CE benefits from the further development of QCAD Pro or QCAD/CAM.
See GitHub commits for the QCAD project.