Why a Unix-Like System?
It is necessary to be compatible with some widely used system to give
our system an immediate base of trained users who could switch to it
easily and an immediate base of application software that can run on
it. (Eventually we will provide free replacements for proprietary
application software as well, but that is some years in the future.)
We chose Unix because it is a fairly clean design which is already
known to be portable, yet whose popularity is still rising. The
disadvantages of Unix seem to be things we can fix without removing
what is good in Unix.
Why not imitate MSDOS or CPM? They are more widely used, true, but
they are also very weak systems, designed for tiny machines. [...]
Why not aim for a new, more advanced system, such as a Lisp Machine?
Mainly because that is still more of a research effort; there is a
sizeable chance that the wrong choices will be made and the system
will turn out not very good. In addition, such systems are often tied
to special hardware. Being tied to one manufacturer's machine would
make it hard to remain independent of that manufacturer and get broad
community support.