One thing that is missing here is a discussion of how a lot of good professors have a strong incentive not to use open source books: Many of them wrote the ones

One thing that is missing here is a discussion of how a lot of good professors have a strong incentive not to use open source books: Many of them wrote the ones they are using for their course. If a professor wrote a good course text then they have a strong financial incentive to make the current edition mandatory for the class. Dealing with this will require some tense negotiations and possibly mean that the school will have to either buy out the books, or adjust contracts to include the copyright to faculty authored content.