The term orphan works is a common term in copyright parlance and it means works for which the copyright owner may not be located. It applies to all works from images to text and includes posters and photographs and letters. In the U.S., there have been several failed attempts to pass special legislation for the use of orphan works. Such legislation would allow those who undertake due diligence to find a copyright owner but are unsuccessful, to use that work in certain specified conditions. It is possible that legislation will be introduced again in the U.S. in the Fall of 2009.
Canada has had an orphan works provisions for many years now. It is called the Unlocatable Copyright Owner provision and is administered by the Copyright Board of Canada. If you cannot locate a copyright owner, and have exhausted your efforts, you may apply for a limited licence from the Board for your use. Further info is at http://www.cb-cda.gc.ca/unlocatable/index-e.html.
Canadian Copyright Law
5 years ago