TurboCNC
EMC2 (Linux)
KCAM
Son los mas usados.
Y encontré esta lista:
EMC2 - Linux
AXIS - GUI for EMC2
KCAM - Windows 98
TurboCNC - DOS
Mach2/3 - Windows 2000/XP
DeskCNC - Windows
CNCZeus - DOS
Master5 - Windows 95/98
DesKAM - Windows/DOS
CNCPro - DOS (recently opened sourced)
USBCNC - USB controlled CNC
CNCDudez - Another USB controlled CNC