While this legislation doesn't answer the question about these open source e-textbooks it does get the idea going. I told the asker that there are other reasons why someone may write such a text. For example for their promotion and tenure, using the ebook as part of their own publications. Or another option would be to have a whole department write a book, this could help meet the unit goals along with having publications for multiple faculty and then producing a text that is focused to their program. The creation of such open source texts could also be used to build notoriety and name recognition if the ebook is good and becomes used elsewhere - possibly then causing participating faculty to get consulting jobs. Another point was made that just because the book is free doesn't mean that everything has to be free. As Seth Godin points out in Free Prize Inside, providing something for free, can mean selling something else. One model for open e-textbooks, is to provide the electronic textbook version for free, but sell associated materials, such as study guides, test banks, presentation collections, etc.
This will also though mean that colleges and universities will need to become more aware of publishing options and may have to start policing their faculty publications concerning textbooks, as with today's technology, just about anyone can put something together and call it a textbook.