California Open Source Textbook Project
The California Open Source Textbook Project (COSTP) was founded in 2000 by Sanford Forte, a former college textbook publishing executive. COSTP was a not-for-profit, collaborative, public/private undertaking originally created to address the high cost, content range, and consistent shortages of K-12 textbooks in California.
Source: Wikipedia — California Open Source Textbook Project (CC BY-SA 4.0)