Copyleft:
Copyleft is a play on the word copyright to describe the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work. In other words, 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. -- Wikipedia
Creative Commons:
"Creative Commons is a nonprofit orgaization that develops, support, and stewards legal and technical infrastructure that maximizes digital creativity, sharing and innovation." -- Creative Commons website
Creative Commons Licenses:
"Creative Commons copyright licenses and tools forge a balance inside the traditional “all rights reserved” setting that copyright law creates. Our tools give everyone from individual creators to large companies and institutions a simple, standardized way to grant copyright permissions to their creative work." --Creative Commons website
Open Educational Resources (OER):
Open Educational Resources are teaching, learning, and research materials, in any medium, that reside in the public domain or have been released under an open license that permits no-cost access, adaptation, and redistribution by others." -- Creative Commons website
Why Open Education Matters from Blink Tower on Vimeo.