Did you read the last two or three pages of the ruling? It basically takes the argument that such things as the pledge, daily prayer, national motto, etc. are not subject to the Establishment Clause because "rote repitition" has stripped any religious meaning out of them, and they are simply done to convey the solemnness of the situation. What a load of crap. The Founders would hang these justices for treason.
The door of the Supreme Court building depicts great events in legal history-- Moses, Hammurabi, Justinian, the Magna Charta, etc. The Ten Commandments are not singled out as representing one true religion, to the exclusion of others. (The 11th Circuit's decision in fact discusses permissible and impermissible displays of the 10 Commandments.) In fact, the Supreme Court doesn't even show the text of the Commandments, only the outlines of the two tablets.