When Apple tried A/UX he was on his way out and it was never an attempt to replace Mac OS.
Regarding NeXT, the company was targeting the new workstation market, which was moving away from Lisp and Ada Machines into UNIX ones, thanks to UNIX code being freely available, as AT&T was not allowed to charge for it.
NeXT main competition were Sun and Irix workstations, so a certain compatibility with UNIX was desired.
However the whole Mach stack was very UNIX-unlike. Many naysayers regarding Objective-C use for systems programming aren't aware that even NextSTEP drivers were written in it.
So it was all about business, Steve was always keen on how Xerox PARC OSes used to work.
When Apple tried A/UX he was on his way out and it was never an attempt to replace Mac OS.
Regarding NeXT, the company was targeting the new workstation market, which was moving away from Lisp and Ada Machines into UNIX ones, thanks to UNIX code being freely available, as AT&T was not allowed to charge for it.
NeXT main competition were Sun and Irix workstations, so a certain compatibility with UNIX was desired.
However the whole Mach stack was very UNIX-unlike. Many naysayers regarding Objective-C use for systems programming aren't aware that even NextSTEP drivers were written in it.
So it was all about business, Steve was always keen on how Xerox PARC OSes used to work.