Also, please don’t conflate paid software with proprietary software. You can pay for either, but only proprietary software is the issue.
Support doesn't work for many small companies, because you just don't have the manpower, so proprietary software is necessary.
Hah, what am I saying, ignoring incentives like that is easy and commonplace, I'm sure they pay it no mind at all.
You can probably make money by selling Windows binaries of OSS software. See ntopng, where compiling on Windows is not that straight forward as compared to Linux.