The laws, including those referenced in the link above, all refer to "motor vehicles' or similar wording. I don't know of any states that have written laws that exempt motorhomes. But in practice (case law), courts everywhere have held that there is a distinction between the driving area and the rest of a bus-type vehicle, including motorhomes. The, "home" aspect contends with the motor vehicle aspect and courts everywhere have ruled that the "motor vehicle" restrictions do not apply to areas designated for other uses. Just where the line is drawn, however, remains a matter of interpretation by both LEO and the courts and is done on a case-by-case basis. For practical purposes, I think you can say the "home" part of a motorhome begins a few feet behind the driver seating.
States that have laws that specifically address passenger behavior can be somewhat more problematic. Again, there is some interpretation as to whether a person riding in the living area of a motorhome is a "passenger" or simply someone enjoying his temporary home. In most cases the question won't ever arise, but if the behavior is flagrant enough to attract attention, the law might be applied by a LEO and it will be up to the courts to determine after that.
