[apotheon]

Let's not forget other more recent stuff that still happened before AtomOS, like Redox. I seem to recall seeing a couple others recently as well, but for some reason I'm drawing a blank now. I think the big deal about this is mostly just that it's an effort outside of Microsoft to do this, and compile it to machine code rather than just use some kind of "higher order" OS that needs to run on top of something else -- and even there it's not unique, even if it looks more interesting than FlingOS (which is evidently just a new take on the "toy kernel/OS for teaching" idea).