Mach4 is described as 'is our newest version of CNC motion control software. Mach4 was written from the ground up to be expandable, flexible, and extremely responsive for use with very large files' and is an app. There are four alternatives to Mach4 for Linux, Windows, Mac and Blender. The best alternative is LinuxCNC (the Enhanced Machine Control), which is both free and Open Source. Other great apps like Mach4 are Blender CAM, PyCAM and Mach3.
PyCAM is a toolpath generator for 3-axis CNC machining. It loads 3D models in STL format or 2D contour models from DXF or SVG files. The resulting GCode can be used with EMC2 or any other machine controller.
Mach3 is very popular among the Hobby CNC community. Artsoft produces Mach3 software and has been around for some time. This software can be used as a fully functional CNC control or used as a CNC simulator for training, learning or testing CNC programs.