Mesa can be used on other operating systems. See https://www.phoronix.com/news/Zink-Windows-Kopper-Progress for an example of using its OpenGL-to-Vulkan translator on Windows.
It weirdly sounds crazier than it is. Mike is an absolute legend for all of his work on Zink.
Edit: Clicked on your link and they are directly talking about work there. Serves me right for not reading it first.