in the Aruba Licencing System
# of Active AP = # Min Licences (AP , PEFNG, WIPS)
so the best is to get
AP licences= PEFNG licences.
in general PEFNG licence is not requested but very recommended, and in your case it is requested (for the guest and the guest logon roles)
if you have more than one controller you can use Licencing server.