What is the definition of a amateur driver?

[Kirby's Ace]

An amateur driver by definition is one who accepts no material rewards for his drives.   

Then how can a driver who drives in these amateur races drive in overnight races on horses he owns and trains?

[kooter for hipin]

Then how can a driver who drives in these amateur races drive in overnight races on horses he owns and trains?

Any monies are given to charities of his choice or otherwise distributed. He can drive in races for pay and receive money but it must first be declared.  You can be both an amateur and professional in this sport.