Question

If I set up a Github project for a toy /prog/ OS, would that be a thing that people are actually interested in contributing to?

OS programmers are some of the most anally retentive people on Earth, especially when it comes to system design. That's why there are 10,000 OS projects rather than much contribution.

You notice that Linus Torvalds/Theo de Raadt are both major arseholes? Because that's the only way you get people to play nicely together.