The pilot's unintentional activation of the green jump light before the airplane was properly configured and slowed for a jump and the jumpers' improper decision to continue with the jump after they recognized that the airplane was at a higher-than-normal airspeed. Contributing to the accident were the pilot’s failure to recognize that the amber light remained on after the first jump and the senior jumper's decision not to inform the pilot that the amber light remained on following the first jump.