[eadan]

It's far from comprehensive, but here are a handful of operating system projects that have caught my eye:

[1] MezzanoOS, an OS written in Common Lisp (https://github.com/froggey/Mezzano)

[2] SerenityOS, a Unix-like OS (https://github.com/SerenityOS/serenity/). The primary author has a youtube channel (https://www.youtube.com/c/AndreasKling/)

[3] RedoxOS, a microkernel OS written in Rust (https://www.redox-os.org/)

[4] Nebulet, a microkernel based on webassembly (https://github.com/nebulet/nebulet)

[5] It was never released by Microsoft, but Midori OS had some fascinating ideas like software isolated processes, asynchronous message passing and object capabilities. Nice write-up about the project by Joe Duffy here http://joeduffyblog.com/2015/11/03/blogging-about-midori/

[pjmlp]

As addendum Midori was used by Bing in production.

> While never reaching commercial release, at one time Midori powered all of Microsoft’s natural language search service for the West Coast and Asia.

https://www.microsoft.com/en-us/research/project/singularity...

And although not quite the same, at least Singularity's code is available.

The WinRT .NET 8.x compiler was based on Singularity's way of compiling[1][2] and UWP .NET Native kind of had some learnings from Midori [3].

[1] - https://channel9.msdn.com/Shows/Going+Deep/Mani-Ramaswamy-an...

[2] - https://channel9.msdn.com/Events/Build/2012/3-005

[3] - https://channel9.msdn.com/Shows/Going+Deep/Inside-NET-Native