Licenses are configurable at the Site level and in the present state only system administrators can do this. Currently, the available licenses are:
Limited – with this license one can assign Limited Site role to users and Limited Circle role to teams and users. Generally gives limited viewing rights to the users with the role. See Site roles and Circle roles for more explanation.
Admin – with this license one can assign Site Administrator role to users and as the name suggests, the role gives overall rights for managing the Site.