4. Fair Use: Transformation
A recent emphasis of the courts has been the idea of transformation. Transformation means that the way in which the work is being used is significantly different than the original use for which it was created. In many cases a transformative use of a copyrighted work will strongly favor a determination of fair use.
There are two ways in which a use can be transformative. First, you could actually make changes to the original work in order to use it for a new purpose. An example would be to take short clips of popular movies and remix them to create a video for the purpose of social commentary or teaching.
The second form of transformative use does not require that you alter the original work in any way. Instead, you simply use the work for a purpose that is significantly different than the use for which it was created. An example of this would be electronic reserves or course readings, where part of a book that is originally sold for mass market entertainment/information is used for the purpose of teaching and research.
Watch Remix Culture to see an example of remixing that falls under fair use.