This is not strictly ReactOS development per se but I used a large amount of ReactOS code and it's at least spiritually related to ReactOS, so I'm cross-posting this here to see if I get more comments. Below is the original message I posted on the seL4 mailing list:

For the past several months I have been working on a project which is to implement a Windows NT personality for the seL4 microkernel, which I have now taken to call “Neptune OS”, named after the codename for Windows 2000. The project has reached the point where I have implemented enough NT primitives such that a keyboard driver stack (taken from the ReactOS source code) can be loaded (as a user process on seL4), as well as a command prompt (shell), which is also taken from the ReactOS source code (albeit a very early version of ReactOS). These are all kernel-mode Windows device drivers that I’m running as user processes under seL4. The goal is to demonstrate that with modern progress in microkernel design it is indeed possible to realize the original NT design as an object-oriented, message-passing based client-server model microkernel OS (allegedly NT was originally going to be a microkernel, as seen in the NTOSKRNL code that has a ke layer and an ex layer).

The project is now on github: github.com/cl91/NeptuneOS. The entire system fits in a floppy (download link: github.com/cl91/NeptuneOS/releases/tag/v0.1.0001).

Check it out! I think it’s cool! For the next release I’m planning to port the PCI stack, the AHCI stack, and a basic file system (probably fastfat.sys).