With the exception if Mach3 running on a parallel port, just about all hobby controls rely on their motion controller for the "real time" stuff. Windows is not an issue at all. I've been using machines costing well over $100,000 with Windows based controls for nearly 20 years, and I've never seen Windows cause an issue.
I would not want a machine control that didn't run on a PC, as you lose all of the advantages that having a PC at the machine brings.