One of the most important aspects of OER is that they carry legal permission for open use, which is typically defined in terms of the 5R activities (Retain, Revise, Remix, Reuse, and Redistribute). Open use is possible when: 1) a work is in the Public Domain or 2) a creator has assigned an open license to their work. The most widely used type of open licenses are the Creative Commons (CC) licenses.
There are, of course, free educational resources that are not OER because they are not openly licensed. "Free" and "open" are different things. (Just because a resource is freely available online does not mean that it is an open resource.) Resources in this category include:
There are also "low-cost" educational resources provided by commercial publishers (increasingly offered as part of automatic textbook billing or inclusive access programs - see sidebar for more). These resources can include proprietary (copyright-restricted) content from the publisher or a mix of OER and proprietary content that the publisher then packages and rents to students at a relatively low cost.
The "affordable course materials" landscape therefore includes OER, free-but-not-open resources, library-licensed material, and paywalled, commercially-published (or (re)packaged) content. All of these resources can lower costs for students, and the non-OER options may be useful alternatives when using OER isn't feasible.
However, OER are the only type of resource in this landscape that permit editing, customization, and unrestricted printing, sharing, and retention. Additionally and importantly, OER do not lock us into contracts or relationships with commercial publishers that reduce choice and undermine academic freedom; nor do OER collect or share students' personal data.
The chart below compares features across several types of affordable course materials. The center column focuses on OER; the advantages of OER over other types of affordable materials are clear.
