Linux has decimated Windows in the server market. It would be unthinkable for a new project to use Windows server, even Azure assumes you want to use Linux.
There are lots of industrial applications where open source has dominated the market. As the end user you might not see it, but almost all software and digital infrastructure you use has open source components.
That chess game even predates OS X, it was a tech demo that came with the NextStep OS and has barely changed since the mid nineties. At this point it would be said to see it go.