IANAL but dont think so - otherwise all self driving car companies would be illegal :) I would imagine this doesn't make it anymore illegal than modifying your tires/suspension/ECU does. It most likely voids your manufacturer warranty while this thing is hooked up.
Obviously IANAL either. But it appears to me that self driving car companies acquires permits/exempts for their highly modified production vehicles from the state DMVs to be able to drive on the public roads. And most of them have to submit year-end reports [1][2] Geohot's comma.ai (mostly himself) had tried to pull this off in 2016 but no avail.[3]