This would fall on the Purchaser or the user of the licensed item to express the Validity of their permission to use.
Such as we require Porters,etc to upload a Permission text when uploading a ported skin.
The authors responsibility is to to police those who haven't received permission, and offer a permission Grant to those who have received said permission/license.
To ask authors to constantly update each skins desc as it is licensed to others would be a huge burden and possibly diminish the amount of given port requests, as they would have to constantly go and edit the desc's over and over.
