Public domain works are not restricted by copyright and do not require a license or fee to use. Public domain status allows the user unrestricted access and unlimited creativity!
There are three main categories of public domain works:
Congress has passed a series of laws extending the term of copyright. Currently, the default term is life of the author plus 70 years. That means that most of the copyrighted works created from the late 1970s to the present may not become public domain during your lifetime.
In general, works published after 1977 will not fall into the public domain until 70 years after the death of author, or, for corporate works, anonymous works, or works for hire, 95 years from the date of publication or 120 years from the date of creation, whichever expires first.