On the one hand I really like the idea of keeping incidental costs of education down by doing things like making textbooks available for free. On the other hand I'm mature enough to realize that nobody is going to create a (quality) textbook for free*.
So my concern for the long-term sustainability of this model is this:
1) One-time grant money is made available to create a free textbook
2) The free textbook reduces the profitability of the proprietary books, which then leave the market
3) Since the money in step #1 is one-time, and since grantors looooooooooove to fund New Awesome Advances but hate to fund Ongoing Operating Expenses, Maintenance and Upkeep the free textbook languishes
3.1) Making non-trivial changes to the textbook is a huge undertaking, so the already-overworked teachers using the book won't be making wholesale revisions to it regularly
3.1.1) Maybe I"m wrong on 3.1, and I've love to see links to projects that contradict 3.1
4) The textbook market is now gone but the free textbooks aren't being maintained either.
I'd love to hear discussion on this, but I'd particularly like to see established, free textbooks that are genuinely self-supporting.
* Yes, yes please do feel free to reply to this post with whatever online, free books you know about. I look forwards to seeing your list