My understanding had always been that each room at the government rate has to be occupied by at least one person entitled to that rate, but I don't remember seeing this stated on the site. I guess I thought it was implied by the T&C saying that you have to be able to show a government/military ID at check-in to be eligible for the discount (although I know they don't always check). I suppose it would make sense though to allow an additional room, for instance, for a family travelling PCS.

As to another rate, the Senior Discount rate, that one allows the Senior (62 years old and over) to book up to two rooms with the 15% discount, see T&C. I've been told this was to accommodate if the senior was "sponsoring" family/friends.