According to Creative Commons, OER are teaching, learning, and research materials that are either (a) in the public domain or (b) licensed in a manner that provides everyone with free and perpetual permission to engage in the 5R activities:
Open Education by Creative Commons is licensed under CC BY 4.0.
OER can be any type of material or resource used for teaching and learning that is free to use and/or alter.
OER include many types of resources in different media and formats:
Types of OER by Sarah Guy is licensed under CC BY-SA 4.0.
A brief intro to the what, why, and how of OER.
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.