No GodotOS is not another Linux distribution or desktop environment, it's an open source fake operating system interface made in Godot Engine, designed to push the limits of UI design in Godot. It's also just really cool.
From the project page:
Welcome to GodotOS, an operating system interface created entirely in Godot! Browse folders, edit text files, view images, play games, and more in one cohesive polished interface that can even be used on the web!
GodotOS is more of a toy than a serious project. It's meant to push the limits on UI design in Godot while creating a desktop that is minimalist, distraction-free, and aesthetically pleasing.
Aside from that, GodotOS is also meant to be a hub for small games and experiences that can easily be bundled in.
If you have a small game / experience you want to add into it, they're also accepting contributions. I love crazy experimental stuff like this, especially when it's open source (AGPL-3.0 license), because it allows people to learn from it and UI design is something that can be tricky to get right in any game engine — so perhaps game devs from all over might want to take a look at this.
I just thought it was really cool and thought you might think so too.
Heck, it is even has a trailer: