'Open source' refers to systems and software products that are freely available online to all users and for which the source code is freely available for use, modification, and re-distribution.
'Public availability' or 'open access' describes webpages and information items that are freely available to anyone with internet access.
'Open access research' is a term used to describe research published by the academic press that has been made freely available (not behind a paywall) online, in the open access environment.
"That which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers." From the Fourth International Conference on Grey Literature, October 1999
Grey literature resides in the open access environment – it is created to be freely available to the public (it is NOT produced by the commercial and/or academic press).
Grey literature is an umbrella term that covers many types of information sources and many different information products.
•Sources: Grey literature is produced by organizations whose primary function is NOT publishing. Such sources frequently used in social work include governmental entities, professional organizations, advocacy organizations, research institutes, and think tanks.
•Products: Reports, commentaries, white papers, press releases, policy briefs, FAQ’s and data sheets, conference proceedings, power points, and lots of other stuff
White Papers fall under the grey literature umbrella and are a type of authoritative reporting that typically cover governmental, social, or consumer issues. White papers are prepared by governmental agencies, professional organizations, public policy and research organizations, and commercial enterprises. By definition, they are based upon an exhaustive research process and frequently address new, controversial or developing trends, programs or products.
“… think tanks are private organizations that emphasize the creation and dissemination of information in the form of policy ideas and advice. Their mission is to win the political war of ideas that surround policy making. Advocacy think tanks do not attempt to present neutral information; rather, they are aggressive ideological advocates for specific policies.
“Advocacy think tanks mostly repackage existing research on policy issues, adding their own ideological spin in order to present their policy ideas in the best light possible.”
Think Tanks. (2007). In G. L. Anderson & K. G. Herr (Eds.), Encyclopedia of Activism and Social Justice (Vol. 3, pp. 1369-1372). SAGE Reference.