Title: GNU General Public License
Course: CIS 121: Linux/UNIX I: Fundamentals ~ For IGNITE Review > Section: Learning Modules

More and more software is being released under the GNU GPL (in 2006 Java was released under the GPL). This license (v2 and v3) is the main license endorsed by the Free Software Foundation. Its main characteristic is the copyleft principle. This means that everyone in the chain of consecutive users, in return for the right of use that is assigned, needs to distribute the improvements he makes to the software and his derivative works under the same conditions to other users if he chooses to distribute such improvements or derivative works. In other words, software which incorporates GNU GPL software, needs to be distributed in turn as GNU GPL software (or compatible, see below). It is not possible to incorporate copyright protected parts of GNU GPL software in a proprietary licensed work. The GPL has been upheld in court.

(Source: Linux Fundamentals, by Paul Cobbaut)