Granted, Boalt won't post their new application till September, and they won't let you have their old one, so Ruskiegirl may be the only one of us who's actually SEEN their application, and it may say you have to write more than one, and if so, disregard everything I just said.
as I understand it, Boalt requires a general PS (up to 4 pages), and also has an optional "Diversity Statement," for which i assume they want to know why you are diverse enough for them to overlook your low GPA when admitting you.