Again, I am a little confused about the general tone of the responses here. Just because the owner of the business may be operating without the proper dealer's license doesn't mean that the OP knowingly participated in any kind of illegalities nor does it mean that he shouldn't be paid his commission.

I agree that if he sues the guy in small claims court he may have a hard time collecting a judgement, but there is no reason why he shouldn't go ahead and do it anyway.