I can't test it but from what I can work out it's the standard Pacejka physics model with a few extra methods to pre-configure it. Like somebody has taken a Mars bar, sprinkled hundreds and thousands on it, then put it in a new wrapper and is selling it to you - except in this case the mars bar was originally free.
Pacejka is the library used by a lot of indi's doing car physics in games that aren't really about cars, it 'suffices' rather than gives you an accurate car physics model - and what this group appears to have done, as far as I can work out, is to set it up for you to make it more useable and intuitive and added some hooks in to give you commonly used data, such as tyre deformation.
I'm making some assumptions in saying this as i'm not in a position to make a more informed judgement, and frankly i've never liked Pacejka either as a programmer or a games player.