Addon User's rights

I am developing an Addon Solution that uses the Invoice Business Object. I want to know if I can use an Addon User Licence or I need a Professional User Licence.

In general, the "rights" that are refered at the "License Comparison Chart" of the "License Guide for SAP Business One 2005" are applied when the user logs on using the standar SBO interface or even when he uses an addon that manipulate various Business Objects through the DIAPI?