FDL Math Textbooks?

PyTHON71 asks: "I'm working through Schaum's Outlines of College Algebra. So far, in chapter 17 (conic sections), I've found 6 errors! Since I can spot them and correct them, I'm not worried about myself. But without math, you can't hack, and if young hackers are getting hung up on stupid math mistakes made by textbook authors... well, it's obviously a case for FDL textbooks. Are any textbooks being produced under the FDL?"