score:5
There is no requirement that a taxi taking you TO Pearson airport be licensed, except in the general way that all taxis should be licensed if they act as taxis.
There is a special requirement that cabs picking you up FROM the airport be licensed by the GTAA, which is described on the site you linked to. That is because a) picking up arriving passengers is when most of the scams happen b) they can check on it (it's almost impossible to police dropoffs).
If you have ordered a taxi from a licensed taxi firm to take you to the airport then you are not breaking any laws and neither are they. They don't need a special license.