The TRUE TEMPERAMENT™ Fretting System is a revolutionary new way to construct guitar fingerboards which tune accurately along the whole neck.
TRUE TEMPERAMENT™ does not imply Just Intonation. It is physically impossible to implement Just Intonation in more than one specific key (and its relative minor) on any instrument with only 12 intervals in the octave. (Except perhaps for computer-controlled instruments using electronically generated sounds.)
What we mean by TRUE TEMPERAMENT™ is that our fretting system will give you super-accurate intonation over the whole fingerboard in the temperament it is constructed for.