Open Source Math Textbooks

In preparing for the arrival of my Monarch, I am seeking Open-source math textbooks. Though these are semi-accessible, they will help sighted teachers who need to find examples to work with, and books that they can safely share or convert without worrying about violating a copyright.

is the first resource I’ve got.
If you are in K12, of course you also have Nimac access but I’m in higher ed, so I do not.
One of my buddies has worked hard to make these books more accessible, so though they are PDF files, many images are described. Images can also be lifted and converted to tactiles, again without fear of copyright violation.
At least now we have a source of middle, high school and college level math we can freely use when playing with our Monarchs!

Another resource:
Math - OpenStax
Supposedly some of the textbooks do use Math-ML when chapters are viewed on the web. I’ll have to confirm that, but even if accessibility is lacking, at least examples are here that can be freely used.