This indicator (the Airbag off indicator light) alerts you that the passenger's front airbag has been shut off because weight sensors detect about 65lbs (29kg) or less (the weight of an infant or small child) on the front passenger's seat.
I am not sure if it is a law in United States (Or CA) that child seat cannot be placed on the passenger's seat in the front.
However, Honda takes a step up to prevent small child or infant to be hurt because of the airbag deployed.