http://about.jstor.org/news-events/news/jstor%E2%80%93free-access-early-journ...
This release of early journal content looks like a generous move on the part of JSTOR, but in fact it's at least partially a response (even thought they deny it) to the uploading of this content to Pirate Bay by Greg Maxwell (http://www.readwriteweb.com/archives/33_gb_of_scientific_papers_-_and_a_manif.... Quite simply, JSTOR would have looked foolish trying to enforce copyright on public domain files, so they did the right thing and opened access to the files with a positive PR-spin.