I am surprised by some comments here that assume that the interim report states the illegality of the flight.
I don't read any of that in the report.
It says that, if the flight was organised as a cost sharing flight, the FAA rules would apply ; i.e. pro-rata cost sharing and common purpose.
However, it is pretty obvious that the costs were neither borne by the pilot nor by the passenger.
Possibly by the operator or by a third person.
As the operator does not hold an air carrier certificate, this is a PART 91 flight.
As per FAR §61.113, in such a situation and if the aircraft transports passengers or goods, the pilot MUST hold a CPL licence.
If the aircraft were not carrying passenger or goods (eg: a ferry flight) and the pilot were not receiving any compensation, the flight would have been legal.
So the conclusion is the same : the flight was very probably illegal because the pilot was not holding a commercial licence.
However, this is inferred from other elements than just the report contents.