That tag simply says it was not intended for street use. It does not say is was not legal. As long as it had lights and signals, ain't much they could do about it.
It also states that it has ZERO warranty! It was a drag car. A bad *** one at that. But not a street legal car. Just like the new COPO camaro. Anything can be driven on the street, just as long as you dont get caught!