Actually Warner Brosthers/7 Artists own the name/image combination road runner. Ma had to lease the rights for it to produce the car. The internet provider use the actual cartoon and therefore would pay the royalities to WB.
A neat story was when the GTX was a success in the muscle car industry, the designers wanted a cheap, stripper version that they could sell to the everyday kids. The GTX was upscale and carried a large price, which most kids couldn't afford. The designers built the stripper version and reluctantly agreed to the name. However they stood firm that no cartoon character was going to be stuck on the car to make it a joke. It was at the actual unveiling to the press that one of the Ma marketing guys (his name escapes me now) had the decals in his pocket. When the car was prepared to be unveiled he quickly stuck them on near the emblems. At that time Chrysler did not have the rights to the name and Warner Brothers wanted what was thought to be a huge amount for the use. The overwhelming impression of the press was enough to convince Ma to get the rights for the character to market the car. Chrysler thought they would be lucky to sell 4,000 road runners in 1968. They sold better than 44,000.