public domain
Not subject to copyright.
There are three ways a work can enter the public domain: if the copyright expires, if the copyright is intentionally forfeited by the owner, or if copyright was not applicable in the first place.
If a derivative work is created based on public domain material, there is a separate copyright for that derivative work which belongs to the author of the derivative work.
Also see: copyright, derivative work.
» For additional information, read our article Copyright 101 for Indie Authors.