tkCNC Editor is described as 'text editor, specialy designed for NC code (G-code) editing for CNC machines. It is used by CNC programmers and operators for fast editing and control of NC code'. There are three alternatives to tkCNC Editor for Windows, Linux, Mac and Blender. The best alternative is Blender CAM, which is both free and Open Source. Other great apps like tkCNC Editor are PyCAM (Free, Open Source) and ECam (Paid).
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.
ECAM is a programming system for CNC lathes and machining centers. He combines features of CAD / CAM systems with typical features of conversational programming. It is not necessary experience with CAD/CAM systems to use this software.