GPL and copyleft license
GPL:- What is GPL?
The term GPL has a great importance in the world of Open Source. The General Public License (GNU GPL or simply GPL) is a widely used free software license, originally written by Richard Stallman for the GNU project. Linux is written and distributed under the GNU General Public License which means that its source code is freely-distributed and available to the general public.
The licenses for most software in Microsoft Windows are designed to take away your freedom to share and change it ð By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software to make sure the software is free for all its users :).
What is Copyleft:- 
Copyleft is a play on the word copyright to describe the practice of using copyright law to remove restrictions on distributing copies and modified versions of a work for others and requiring that the same freedoms be preserved in modified versions. Copyleft says that anyone who redistributes the software, with or without changes, must pass along the freedom to further copy and change it. Copyleft guarantees that every user has all the freedom as mentioned in the previous post. You may charge money for all this too.
Your name will stay for ever in the license ð
All rights reversed.
Only restriction on a first review is “You cannot change or alter the license”
List of Free and non Free licenses are listed at
http://www.gnu.org/licenses/license-list.html
A comparison of Open Source Licenses can be found at http://developer.kde.org/documentation/licensing/licenses_summary.html
