Yes, it all sounds "brilliant" -- but I don't see any progress. They talk about replacing all their textbooks in 5 years. Come on. Someone is going to write all the books a state needs for K-12, and give them away? Sounds like this has pretty much stalled.
Drew is right. This project is dead-in-the water. It really is abysmal.
If you look at the project it appears that all of the elements for success were in place. This should have worked. So why did it fail? I think you can fix the blame on the California Curriculum Development & Supplemental Materials Commission. They are the body responsible for making the rules as to what passes for an acceptable textbook for use in California schools. These rules were an albatross around the neck of this project. I should have seen this last year when I declared the concept to be "brilliant!"
What are the lessons to be learned here? Open beats closed. The California Open Source Textbook Project might have embraced open source technologies, but the requirements imposed by the the Commission in essence turned the entire project into a closed platform. Rather than write to the closed specifications of the Commission, the people chose to disintermediate the control-freaks by self-selecting into the more open effort.
This project shows that it doesn't take much to destroy the conditions by which open-content projects work. If California is truly serious about migrating to open-content textbooks then they need to be willing to let go of the rules of the past. You can't expect new and interesting things to happen while clinging to the rules of the last century.