Copyright protects the original works of authors for their life time, plus 70 years. There are some exceptions for anonymous, pseudonymous, or works made for hire which last for 95 years from its first publication or for 120 years from the works inception depending on whichever happens first.
Under the Fair Use Doctrine, certain conditions must be met in order to use copyrighted material without receiving permission or paying royalties to copyright holders. Acceptable use of the Fair Use Doctrine can be determined by meeting four fundamental factors:
These guidelines, can help to discern what uses are considered fair use. However, there are exceptions to the rule.
You can use the Fair Use Evaluator to determine the "fairness of a use under the U.S. Copyright Code.
For more in-depth information visit MS State Libraries Research Guide on Copyright & Fair Use or the U.S. Copyright Office.