There is a machine shop downtown that I setup its network. They were
wanting more control over some of their older computer controlled
lathes so we started messing around with writing new software for it.
There is some software you can download from different machine tools
sites and even from some manufacturers but its almost all windows
based. I looked at writing code in Ruby. You can def do it on linux
but the software will have to be written from scratch - as far as I know.

I did this over 20 years ago with a Commodore 64 and a Bergmaster
multiple turret drill press. Of course, that was a *wee* bit
different. You'd have to build an interface card (maybe you can buy
one? -I had to build it back then) and write a device driver, then
write custom software.

A "device driver" is something I did on the C64, although a "device
driver" in that world wasn't anything like it is in Linux, just some
ML code that was called by a C64 BASIC program. The only reason it was
written in assembler was that it had to run faster than a BASIC
program could.

It worked fairly well, but I'm afraid I'm just reminiscing, I can't be
of much help in the modern world.

http://www.linuxcnc.org/
This is a open source program and based off of Ubuntu. You can DL and use it as
a live CD and see if it works for you.