Though I'm not sure open philosophy needs a 'textbook' per se I still think this is a useful initiative that may grow. Christina Hendricks notes that "We are working with an organization called The Rebus Foundation, a Canadian non-profit that is made up of wonderful people who are doing great things with digital publishing and open textbooks." I've signed up to the Rebus Community and have looked into the philosophy textbook. Note this: "it is free of cost to students. There is no price tag." That is what I call open content. Here's more information on the Rebus textbooks project.