I'm not sure what in the name "fanfilm" would suggest its status as such would be dependent on the number of people involved in making it. It's a pretty self explanatory descriptor
Actually, I'd argue it's not. The descriptors are getting murky.
Is "Renegades" a fan film? Is "Of Gods and Men?"
Is Phase II still a fan production? Is Star Trek Continues? Is Starship Farragut?
At what point does having professional involvement push a fan film out of that arena and into a semi-professional or even professional production?