Why Open Education by David Blake is licensed under CC BY 3.0.
Section 67423 of California Education Code defines Open Educational Resources (OER) as:
"high-quality teaching, learning, and research resources that:
Open educational resources include, but are not limited to, full courses, course materials, modules, textbooks, faculty-created content, streaming videos, tests, software, and any other tools, materials, or techniques used to support access to knowledge."
According to the Community College Consortium for Open Educational Resources, an open textbook: