RAAus documents here.
https://www.raa.asn.au/documents-and...ate-documents/
In a cursory look I'm unable to find any direct statement about the number of passengers that may be carried in a two seat aircraft, though they talk about "passenger" in the singular.
An example - NO PASSENGER IS TO BE FLOWN UNTIL SUCH TIME AS THE TECHNICAL MANAGER HAS ISSUED THE PERMIT TO FLY
Wonder if the required cockpit warning is a get out of jail card - WARNING PERSONS FLY IN THIS AIRCRAFT AT THEIR OWN RISK. THIS AIRCRAFT IS NOT OPERATED TO THE SAME SAFETY STANDARDS AS A NORMAL COMMERCIAL PASSENGER FLIGHT. CASA DOES NOT SET AIRWORTHINESS STANDARDS FOR EXPERIMENTAL AIRCRAFT