I've never made proprietary software. I've written hundreds of thousands of lines of open source code in dozens of projects. I make releases of those projects, answer bug reports and issues, review PRs, all for free. Often I get annoying demanding emails for support for something I give away for free, which is quite annoying, but I usually answer anyway unless the sender is really annoying.
In a couple of them, there are features which are the because they amused me when I wrote them. Nothing that would lead to a wrong answer. Maybe if someone wants to base their business on my free labor, they have to put up with that.