United States copyright law outlines several ways that works enter the public domain, thereby becoming freely useable by anyone: (1) if the copyright has expired, (2) if the author has relinquished his or her right to protect the work, (3) if the work was created by the federal government.

Duration of Copyright

Due to changes in copyright law, it’s not always easy to determine when the copyright on a work has expired. For works created on or after January 1, 1978, the duration of the copyright is the life of the author plus 50 years after his or her death. (This term is somewhat longer for works created for hire; refer to Title 17, section 302 for details.) For works created before 1978, the law is a bit more complicated. But in general, the maximum length of copyright is 75 years after the work was created (see Title 17, section 304 for specifics). With respect to international treaties, Article 7 of the Berne Convention defines the duration of copyright as “the life of the author and fifty years after his death.”

See also…

Intellectual Property and Internet Law

International Law Issues