What is the definining line between a helicopter and a drone a person can ride in?
A helicopter is an aircraft in which thrust and lift are provided by rotors.

A drone is an unmanned, self-piloted or remotely-controlled aircraft, which can use rotors to provide thrust and lift, but can also use other means such as propellers or turbines. 

To put it in simpler terms, a helicopter can only be a helicopter, regardless of whether it has a human inside or not. A drone can be any kind of aircraft.