Copyright terms in the European Union run for the life of the author plus seventy years. Freud died in 1939. So on January 1 2010 all of his copyrights expired in Austria and the United Kingdom. Most countries reflect that lapse in their own law by a provision known as the rule of the shorter term, but the United States doesn't follow the rule of the shorter term.
So I could republish all of Freud's writings from Vienna where they're public domain, but not from the US where they remain under copyright. The Wikimedia Foundation servers are located in the United States. So because the servers fall under United States law, Austrian Wikimedians can't bring Freud's later writings onto the German language Wikisource (which hosts free licensed texts).
United States copyright law is complex, but one rule that holds true nearly all of the time in the States is that material which was published before 1923 is public domain (no matter when the author died). So this 1914 portrait is fine to reuse but a 1924 portrait wouldn't necessarily be free. That copyright gap is going to widen: Anne Frank's autobiography will lapse into public domain in The Netherlands in 2015 but will remain under copyright in the United States. Broadly speaking, United States copyrights are in a holding pattern until 2020. So 1923 works won't lapse public domain for at least another ten years.
For the last thirty years U.S. copyright law has been getting a series of extensions. Those extensions have something to do with lobbying by the Walt Disney Corporation: Mickey Mouse was created in 1925. It doesn't actually protect the value of Mickey Mouse to keep Sigmund Freud under copyright in the United States, though. The United States could adopt the rule of the shorter term without harming Disney's profits.
Other culturally valuable material is getting tied up because of this legal hitch: William Butler Yeats's works entered public domain in his native country of Ireland this year. I can republish this 1911 portrait of him freely, but I can't republish his late poems.
And one thing worth wondering is this: with a normal copyrighted work it could be possible to contact the copyright owner and request a release under copyleft license. How does one seek access to material that remains under a copyright which no one seems to own?