"Copyleft is a general method for making a program or other work free, and requiring all modified and extended versions of the program to be free as well."
Copyright promotes the development of scholarship through respect for the work of others.
Copyright is a form of protection provided by the laws of the United States. It gives the creator of an original work the right to protect his or her work from unauthorized use by others.
Copyright protects any original work of authorship that is in tangible form, regardless of whether or not a notice of copyright 
exists on the work. Tangible form may include anything written on paper, saved to disk (web pages, graphics on the web, electronic mail messages or computer programs, or saved on any audio/video device.
Some items are NOT protected by copyright, such as...