LinuxCNC

LinuxCNC turns an ordinary computer into a real-time machine controller: it reads G-code, generates motion commands for the drives, handles tool compensation, radii and axis synchronisation, and supports non-trivial kinematics such as five-axis machines and robots.

It is the tool behind a large number of retrofits — an old lathe or mill whose original controller died, where the controller is replaced instead of the machine. It runs on Linux with a real-time kernel and needs suitable interface hardware.

What is missing: this is not a half-hour install. Configuration requires understanding the machine and its electrics.