Mach4 is CNC (computer numerical control) software used by FamiLAB on the 4x4 CNC Mill/Router (and the CNC Mini Mill soon). It is commercial software made by Artsoft (a division of Newfangled Software).
Mach4 is the successor to Mach3. While Mach3 was designed for simple hobby machines, Mach4 is meant to provide quality, speed, and the ability to use industrial style controls and methods. Mach4 is offered in different versions, with the standard Mach4 installer able to control mills, drills, lathes, and routers (and more types coming soon).