nixos-bsd.

[Alain De Vos]

Can anyone explain.
- Which kernel does it run linux or bsd ?

https://github.com/nixos-bsd/nixbsd

What is the good the bad the catch .

 

[drhowarddrfine]

That's a version of NixOS. It's a package build system for building packages on top of FreeBSD. So it runs on FreeBSD.