The power user home license is Unlimited I think. However you have to be an active support provider in the forums to get one.
All licenses are based on an "honor" system I think, so you can exceed the number you are licensed for but you will have evil nightmares all the time as guilt eats you up.
Does anyone know what is required to be considered an active support provider? (I am a home user with 26 computers of all makes and models, which I use to keep myself diverse in experience while being employeed in a MS only shop)