Is this default answer Goldelico forces you to use whenever anyone asks about GSM stack? Screw the NSA-free part? I'll answer myself: a phone with FOSS GSM stack is illegal to operate, everywhere except in anarchies where they won't have any network provider to use it in. Please stop spreading false claims here! A GSM stack needs certification and that has to be done even by the network operators. Operating a transmitter is basically illegal everywhere on the world without a licence to do so.