"Open access" is a new publishing model. It is free, unrestricted, online access to scientific and scholarly research. There are two primary vehicles for providing open access: open access journals, and open access archives or repositories.
Do you cite the articles found through Open Access? Yes!
Responsible academics must always cite sources.See: Your Bibliography
In contrast to credible publishers there are unscrupulous companies that project the image of a scholarly publisher but are not. This article in Nature examines the problem and includes information on how to determine what is a "predatory journal."
The following rubric, linked below, is posted to the Loyola Digital Commons. The tool takes users through a thoughtful review of the Open Access source they are considering. The tool is helpful for students who are using Open Access sources for their research, or faculty considering an Open Source publisher.
Rele, Shilpa; Kennedy, Marie; and Blas, Nataly, "Journal Evaluation Tool" (2017). LMU Librarian Publications & Presentations. 40. http://digitalcommons.lmu.edu/librarian_pubs/4