Criteria of a truly open textbook:
- Content is free or nearly free. Free access.
- Easy to access using standard and open source or free applications.
- Easy to copy, parse, and rearrange using available open source software.
- Supplements that are really part of the textbook must meet the same criteria and are provided under the same license.
- Meets attribution requirements specified by the open license.
OER = Open Education Resource
According to the U.S. Government:
Open educational resources (OER) means teaching, learning, and research resources that reside in the public domain or have been released under an intellectual property license that permits their free use or re-purposing by others.*
An open textbook is a type of open education resource.
Many open textbooks are created by independent academic authors who were not satisfied with offerings from traditional textbook publishers, felt the cost of traditional textbooks were too high, became frustrated with the idiosyncrasies of copyright laws, or supported an education system that fostered the freedom to spread academic ideas for the benefit of all.
Most authors use a Creative Commons license on their open works, or a customized copyright with specific uses defined. (See References)