Copyleft is an adaptation of conventional copyright. The copyleft holder retains the copyright, but chooses to release it in a manner to allow (and encourage) wide distribution of the work, and ensuring that redistribution is as easy as possible.

As used in my website, "Copyleft" means "Released under the Free Software Foundation's General Public License." If you have specific questions about the exact terms of the GPL, I strongly recommend you check the following web pages:

http://www.gnu.org/
http://www.gnu.org/copyleft/copyleft.html
http://www.gnu.org/copyleft/gpl.html

The full text of the GPL is available from this site, as well as a discussion of the underlying philosophy. Incidentally, the "Free" in "Free Software Foundation" is a political term, not economic: Think "free speech," not "free beer."

In a nutshell, here are the main provisions of the GPL. This should be taken as an informal discussion of the GPL, not a replacement for it.

1.    This is specifically NOT placed in the public domain. I retain copyright.

2.    Content is provided as is, with no warranty, not even merchantability or suitability for a particular purpose.

3.    Except for redistribution, you may use this material however you see fit, for any purpose you see fit. You do not need permission from me or anyone else to use it, modify it, adapt it, or base other work on it. As a matter of courtesy, I would appreciate an email at bhare@cstp.umkc.edu if you decide to use it, but this is not required.

4.    If you redistribute this work, you MAY:

• charge a fee for redistribution, or not, as you see fit.
• redistribute the original (verbatim) work in any manner, via any medium, provided that my name and the copyleft notice are included.
• redistribute a modified version, provided that your modifications are clearly indicated and that my name and the copyleft notice are included.
• redistribute secondary or derivative works, provided that the work clearly indicates it is based on my work and the original copyleft notice is included.

• restrict the rights of anyone you redistribute it to regarding their use, modification, or further redistribution of the work. Anyone you give or sell it to must be given the same use, modification, and redistribution rights that I am giving you, and you must inform recipients of their rights under copyleft.
• require others to charge for redistribution.
• prohibit others from charging for redistribution.
• require others to collect or pay any royalties for redistribution.
• claim copyright on any work that I have done.

Quoting directly from the GPL: "You do not have to accept this License, since you have not signed it. However, nothing else gives you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License."

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