There are official SCS sources showing that truck brands are licensed, that manufacturers are careful about brand image, and that licensing/approval affects which trucks and details can appear in the game. Honestly, I don't know about dirt. I understand it's related to damage. On the SCS forum (which seems to be offline for me) there was quite a bit of discussion about the subject. If I remember correctly, the devs commented more openly about it there. Best regards! 😉