Copyright, always a confusing area to non-lawyers (and perhaps to some lawyers!) has been further complicated by the Sonny Bono Copyright Extension Act (1998). This act is on top of numerous previous changes in the length of copyright protection made from the early 1900s onward.
Under the latest iteration of the law (1978), works by individual authors were protected until 50 years after the year of the author's death. The Bono extension increases this to 70 years.
The real change, however, is for so-called corporate copyrights (such as Disney's Mickey Mouse), which previously were afforded 75 years of protection, dating from the date of creation. After Bono, protection was increased to 95/120 years. Congress has the power, of course, to increase protection in addition to what Bono enacts.
The Bono Act has been vilified as a favor to the Disney company, which lobbied very aggressively, skillfully (including campaign contributions), and largely without public notice, to protect the character Mickey Mouse and others from falling into the public domain in 2004. Other American icons which will not fall into public domain as a result of this copyright extension include Winnie the Pooh (guess who owns the rights?), the music of George Gershwin, and the Hill Sisters' Good Morning to You/Happy Birthday to You.
Some feel that the Bono extension essentially provides "eternal copyright," something that the Constitution does not grant (U.S. Constitution, Article I, section 8). Justice Sandra Day O'Connor writes: "The primary objective of copyright is not to reward the labor of authors, but 'To promote the Progress of Science and useful Arts.' To this end, copyright assures authors the right to their original expression, but encourages others to build freely upon the ideas and information conveyed by a work. This result is neither unfair nor unfortunate. It is the means by which copyright advances the progress of science and art." Congress has the power to extend protection, however, and when Congress continues to increase protection time, the result is de facto eternal copyright protection.
The same group feels that not making such American cultural "landmarks" available for others to use and develop stifles creativity and discourages innovation.
Naturally, there is the opposing view that an individual's (or a company's) works deserve to be used as the creator sees fit.
Summary of copyright protection after Bono (as I understand it):