In preparation for Open Access Week (October 18-22, 2010), I am sharing this excert from Duke University Libraries. See the full article for more information.
Open access (OA) in its purest sense is making literature free online without any fees or restrictions due to copyright or licenses.
The Budapest Open Access Initiative [http://www.soros.org/openaccess/read.shtml ] was the first to define open access as being publicly free on the Internet, allowing users to read, download, copy, distribute, print, search or link to the full text of articles without legal, financial or technical barriers. Since their statement, others have followed and Peter Suber, one of the true experts on OA, provides an excellent overview and timeline on his Web site: http://www.earlham.edu/~peters/fos/overview.htm