Reportedly, the pilot had previously flown in a 2 place ultralight vehicle, but had not flown in one that was equipped with a canard. He indicated to the owner that he would like to taxi the ultralight. The owner obliged after explaining the operation of the vehicle & being sure the pilot would wear a helmet. The pilot was cautioned to keep his speed below 20 mph so as to avoid becoming airborne. The owner & another witness observed the pilot as he started to taxi down the runway. They stated that the ultralight was zigzagging & that the pilot increased and decreased the power several times as the vehicle would speed up & slow down. The ultralight continued down the runway and became airborne as it traveled over a rise. Witnesses heard a power reduction & lost sight of the ultralight momentarily. An increase in power was then heard & the vehicle reappeared above the horizon. Reportedly, the ultralight pitched up, then pitched down & crashed. The weight shift vehicle had bungees from the seat to the canard. No airspeed gage installed.