Historically, founder's editions are fully loaded and have one price. So I interpret this as being 10% off the price of the car, and 2% for every referral thereafter. At 50, it's free.
Humorously, I suggested a founder's next-gen roadster as a referral award to
Elon 4 days ago on twitter.
My guess is it was already in the works.. but wouldn't it be cool if Elon saw my tweet and said "Hey, good idea!"