here.
http://www.gencourt.state.nh.us/rsa/.../270-a-mrg.htm
Now we've had definitions and discussions re: just what a "houseboat" is but if you can sleep on it ... it's got "sleeping facilities" and no doubt a porta-pottie falls under the ruling of a "toilet facility" (albeit a temporary one).
Frankly if you're tied up at a dock or beached onshore next to a house I doubt the MP will bother to check on you. An anchor in the water and a line to a tree onshore in the woods may not go so unchallenged. I'd have to say Broadhopper got lucky.
(ps - a galley makes no difference whether a boat is a "houseboat")