Coined in 2002 at the Budapest Open Access Initiative as a way to combat the rise in publisher consolidation and access fees.
Library Journal (Smith, K.L. Of Predators and Public Health, May 23, 2013) reported that the American Public Health Association (APHA in SHERPA/RoMEO) recently amended their OA policy to read that rather than a 2-year embargo on articles that were not originally published OA, there would now be a 10-year embargo, so that no articles published in the last decade would be available OA until they were 10 years old, unless they were federally funded and available in PubMed Central.
Which would you prefer: to have your work immediately (or almost immediately) available for use and research, or tucked away in a database for a decade, after which point its effect and usefulness, especially for those who can't afford the access fees, may be reduced?
Creative Commons licenses were created as a way to give authors the ability to make their works accessible online beyond the restrictions of traditional copyright. Authors can assign a range of licenses depending on how they want their works to be accessed and/or reused.
The Open Access Spectrum Evaluation Tool by SPARC (Scholarly Publishing & Academic Resources Coalition) scores journals by their degree of openness, based on the How Open Is It guide. If a journal claims to be open but restricts some uses, it will get docked for that.
Do a lateral search: open another tab and Google the publisher. If nothing comes up other than their own website, that's a red flag.
Here are some tools to help you ascertain whether a journal is legitimate or predatory.