Look for a license, often Creative Commons or GNU, this will give the details on how content can be used, shared, and adapted as well as stating an requirements (such as attribution or non-commercial use). Some material may have instructor content that cannot be shared with students.
Some open access scholarly publishers operate under questionable practices - for example with minimal or no peer review, charging fees after accepting papers, using editor's names without permission. 
If in doubt about the quality of a journal, check if it is a member of the Open Access Scholarly Publishers Association or if it is listed in Ebscohost: Serials Directory or the Directory of Open Access Journals (DOAJ)
For a list of things to look for when assessing journal quality - both positive and negative - see Open Access Journal Quality Indicators at the Grand Valley State University.
1. Predatory open access publishing (2017). Retrieved from https://en.wikipedia.org/w/index.php?title=Predatory_open_access_publishing&oldid=760792711 )
Text a derivative of “How Libraries can Help”, in CCCOER: Faculty and Librarians Selecting High Quality OER, by Tina Ulrich, licensed under CC BY 4.0.
The right to....
*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