A motorcycle is a motor vehicle just like a car. A sword is considered just like a handgun. You can have a handgun or sword in any location of your motor vehicle, including your person, without a GWL, openly or concealed. He is totally legal.
However, if he steps off of the motorcycle in public without a GWL he is carrying a "weapon" without a license, which is a crime in our state.
OCing a sword on a motorcycle is the same as OCing a handgun on a motorcycle, no license needed as long as you don't get off of it in public. Beware of a LEO asking/telling/ordering you off the bike during a trafffic stop.