"Open Educational Resources (OER) are teaching, learning and research materials...that reside in the public domain or have been released under an open license that permits no-cost access, use, adaptation and redistribution by others with no or limited restrictions" (UNESCO)
There have been multiple studies on faculty implementations, misunderstandings, acceptance of, and evaluation of OER.
The Review Project has curated a number of empirical studies published in scholarly journals on the topic. Their general conclusion is:
Several thousand students and faculty members have shared their perceptions across more than a dozen studies that have focused on perceptions of OER. Given that (1) students and teachers generally find OER to be as good or better than traditional textbooks, and (2) students do not perform worse when utilizing OER, then (3) students, parents and taxpayers stand to save literally billions of dollars without any negative impact on learning through the adoption of OER.