I don't know if you'd call it an operating system, but I created a GUI that runs on top of your host OS called AOS-GUI. It can be modified and tinkered with to suit your needs, and it has a package manager so you can install applications made by other users to your system. (written in python for now because I'm lazy, but I'll probably rewrite it in c++ later since it's a pyqt5 app)

Here's a screenshot of the main window:


And here's a link to it if you're interested: https://github.com/AOS-GUI/AOS-GUI/

Nice! Can you change the title bars so they don't look like they are running on the particular OS?

Sure! I'll add this and push it to main after I add some other features.

Looks great! Even outside of calculator parlance, I'd expect something like this to be called a shell.

Very nice! I'd also describe it as a shell. Reminds me of how in 1993 we'd program interfaces for doing stuff because the OS was DOS and it wasn't very cool to type commands to get everywhere.

I have released AOS-GUI version 0.8 beta! (I also released 0.7 but I didn't make a post about it)

Here are some of the things I did to it since the last post:
- i added lots of new terminal commands
- i made a new editor application with python, markdown, and aosh syntax highlighting
- i added wallpaper support
- i created a package manager terminal command
- i smashed a lot of pesky bugs

Also, here's the default desktop wallpaper! It's pretty basic but I think it does the job well.

Looks good!

What are your intended use cases - i.e. who would you recommend it to?

Thanks

I would recommend it to anyone who likes tinkering around with software to make it their own. It's meant to be a "programming playground" of sorts.