[zonidjan]

It was developed from something that was based on Mach. However, it is also based on BSD, as your second link states.

> The BSD code present in XNU came from the FreeBSD kernel. Although much of it has been significantly modified, code sharing still occurs between Apple and the FreeBSD Project.

[asveikau]

The description of "Mach with a BSD layer on top" was nonetheless accurate. When you look at actual BSD you will see it is rather un-Mac-like, so I don't think it is a highly relevant comparison. (The path drawn here from the Purism laptop to XNU is very dubious.)