OER resources, (Open Educational Resources), "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." The 5Rs are retaining, remixing, revising, reusing and redistributing.
Per https://wiki.creativecommons.org/wiki/What_is_OER%3F
