Introduction to Copyright and Licensing
Traditionally, many articles, publications, and multimedia are copyrighted. This means that the creator of the original work is granted an exclusive set of rights to copy, distribute and adapt the work.
It is illegal for other people to copy, distribute, or alter the work unless given explicit permission from the creator.
However, with an increasing population being connected to the Internet, such copyright laws are burdensome especially when sharing text, images, and other media. A number of different licenses in addition to the traditional copyright have emerged and are an increasingly popular alternative to a traditional copyright license.
Some commonly used licenses include the Creative Commons licenses and GNU (GFDL/GPL licenses). In addition to licenses, the creator may also declare their work as fair use or public domain.
Creative Commons
Creative Commons is a non-profit organization known for its creation of the Creative Commons (CC) License. The Creative Commons License are a set of less-restrictive copyright licenses that allow for the sharing and re-distribution of work without requiring explicit permission from the author.
Each of these CC licenses have different terms regarding copying, attribution, and distribution. The icons next to the license stand for the restrictions that the author has placed on the work.
Attribution: Requires that credit to the original author be stated on the distributed or derivative work. (All CC licenses will have this condition.)
Non-commercial: The author does not allow commercial (selling the work, profiting off of the work, etc.) use of the work.
No Derivative Works: The author allows you to copy and distribute the work but you cannot alter or change it in any way, shape, or form.
Share Alike: The copy or derivative work must be licensed the same as the original work's license.
Other Licenses
In addition to the Creative Commons license, there are a number of other licenses that are in use with varying terms of use. Some such as the GNU Public License allow you to redistribute and alter the original work as long as the distributed work is also licensed as GPL.
Other licenses may be more restrictive on what may or may not be done to the work. Be sure to check the image source carefully so that you do not infringe on someone else's copyright.
Public Domain
Things that are in the public domain are free to use without any restrictions. You can copy, alter, and redistribute the work without the need for permission from the author. Keep in mind that most works are not in the public domain even if the author says that there is no copyright; the author must explicitly state the work is public domain.
In the United States, public domain applies to any work created by a federal government employee (not state or local gov't), where copyright has expired (typically 70 years after creator's death), or where the author explicitly releases work in to public domain.
Fair Use
Fair use is a legal clause allows people limited use of a copyrighted material without permission from the creator. Using copyrighted material for educational purposes such as teaching is a form of fair use. However, what constitutes fair use is often ambiguous and it is generally not recommended to claim fair use unless there is absolutely no other alternative.
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