<div dir="ltr"><div class="gmail_extra"><br></div><div class="gmail_extra"><b>tl;dr: </b>public domain works used as illustrations increase traffic and would cost about $250 millions a year to the project had they been copyrighted.</div><div class="gmail_extra"><br></div><div class="gmail_extra"><a href="http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2560572">http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2560572</a><br></div></div>