I don't think they license them at all. Class T is just a digital amp method, there are plenty of people making digital amps which probably use similar methods - eg Apogee were doing small digital chips too.

When I last looked, Tripath weren't trying very hard to get into automotive - they appeared more interested in the home cinema market (the early sony 5.1 DVD player and amp-in-a-box used tripath chips). That may well have changed now though.

Hugo