The most interesting paragraph was that the author is thinking about porting the Kali pentesting suite to OpenBSD. That would be awesome.
And if there is one thing that's less "open" than on Linux, its the OpenBSD kernel.
Dont get me wrong, the source is out there. But you're not gonna find anyone forking it, running patchsets (like almost any linux main-distro does) or the like. Compiling your own kernel isnt even supported.