Update [[http://www.malyansys.com/downloads/gpx-20151119.exe|GPX]] included support for M106 and M107 command:

M106 T0 S100    ; set pwm to 100, max value 255

M107 T0         ; disable pwm



For ReplicatorG, please use M126 T0/M127 T0. PWM function is not supported in ReplicatorG interpreter.