What is a sub-account user? And how exactly does a user license work?

Hi,

Having a sub-account user allows you to give another user access to your forms. Sub-account users can view and edit the forms in your account. You can check this article for further information regarding sub-account users: How to Share Forms with a Sub Account User. With regard to the user license, I think you are referring to the ownership of the content inserted in the Jotform forms. The user owns any material inside the forms and submissions, however if it is made public, Jotform will be granted permission to modify or publish the said forms.

Do inform us if you have any other concerns,
Regards.