Is an owner liable if they allowed an unlicensed drive to operate their vehicle?

Unfortunately, civil liability in North Carolina is not affected because the the operator of the truck did not have a valid driver's license.  That will remain strictly a criminal traffic matter.  Issues such as whether a driver had a valid operator's license, or even if the parties wore their seatbelts are irrelevant in civil cases as regards to negligence.  Sorry the law isn't more helpful to you. I do hope your son was okay.

Because operating a vehicle without a license is a violation punishable by a fine under most state laws.  It is not what the law calls an "indicia of negligence."   In other words, it does not mean that you are a bad driver because you have a license any more than it mean that you are a good driver if you do have a license. And it does not mean that you did anything wrong in the operation of a motor vehicle because you do not have a license anymore than it means that you did not do anything wrong because you do have one.  So if your son was found to be negligent and liable for the accident he is responsible.