The purpose of an OS is to manage the resources of the computer, CPU, RAM, devices, etc. This is simply a UI generated by an NN.
Seriously. :o)
- Lisp/lispm
- Ada/iAPX
- C/ARM
- Java/Jazelle
Most don't really take off or go in different directions as the language goes out of fashion.
Contractors get paid for the time they're not in work.
I've been on both sides and have always been lucky in that I've gone from contract to contract but that is certainly not guaranteed.
As I understand it Mach was based on BSD and was effectively a hybrid with much of the existing BSD kernel running as a single big task under the microkernel. Darwin has since updated the BSD kernel under microkernel with the current developments from FreeBSD.
"Mach was developed as a replacement for the kernel in the BSD version of Unix," (https://en.wikipedia.org/wiki/Mach_(kernel))
Interestingly, MkLinux was the same type of project but for Linux instead of BSD (i.e. Linux userland with Mach kernel).
/s