To my understanding, as the maker of the software, I have the right to dual licensing the software as I wish, be it both an open source license and a proprietary closed license at the same time.
However, I'm unsure about the ramifications if I publish the code on Github under the GPLv3 license, getting some contributions from users that wanted to help fix some issues or add translations, and these changes making it into the proprietary version of the software.
How does it work in this scenario?
For the sake of clarity I'll offer an example, if I am writing software that I plan to release on Windows for free under the GPLv3 license and also plan to release a macOS version for a fee using the same code base under a proprietary, non-open source license, do I retain the right to do that even though the Windows code under GPLv3 has gotten contributions from other Windows users? Naturally, I would have to change some things in the code for it to work properly on macOS but these changes would not make it to the Windows version source code since it's irrelevant to that platform.
I just want to wrap my head around the implications of these and if someone can break down how this would work, I would greatly appreciate it!