The driver takes liability, of course, and this can be used wherever the driver deems it safe and useful.
With the disclaimer that this depends on the location of course. For example, I think in Spain (and probably EU wide?) modifications that affect steering and throttle control would need to undergo local homologation before you're legally allowed to drive with that on public roads at all.
Which, to be honest, makes a lot of sense. I don't think anyone would be happy if cars start using software MVPs automatically controlling throttle and steering while in real traffic.
Suppose I deem it safe and useful for my 6yo to drive for a while, using his Xbox controller from the passenger seat.
It is illegal in many countries for a device (or anything else) to obscure any part of the driver's forward view (area swept by wipers). So even without actually controlling the car, we have an unlawful vehicle.
If you’re so confident this will drive my car into a ditch, then front the money for me to buy a compatible car & this kit. If it drives my car into a ditch, I’ll pay you back double that money.
That’s an easy bet for you, right?
Would you buy an angle grinder that's specifically been designed to not have a guard so it can be more useful, made by random contributors on the internet without any official certification? I'll stick with the ones that needed to pass the CE mark and you can sue the company responsible if it chops your arm off thank you very much. They at least have a required level of anxiety needed to patch anything serious knowing the level of responsibility they carry and what's coming if they mess up.