Open Educational Resources (OER) differ from traditional educational resources in their licensing and permissions. Namely, the “open” aspect of OER can be defined by David Wiley’s 5R Framework.
*This material was created by David Wiley and published freely under a Creative Commons Attribution 4.0 license at: http://opencontent.org/blog/archives/3221
Freely accessible textbooks, generally accessed online. Open Textbooks are part of the larger Open Educational Resources model, an effort to make high-quality learning materials freely available in electronic formats.
In general, open textbooks exhibit the following characteristics:
An e-textbook becomes "open" when its copyright-holder grants usage rights to the public through an "open license." which typically includes the right afforded by the 5 R's of open: the right to retain, reuse, revise, remix and redistribute.
A list of repositories that allows you to search for OER content by discipline, type, level and other criteria.