gpl

GNU Project and Free Software Foundation
One of the founding organizations of free and Open Source software. Home of the GNU Public license and many open source projects including GNU Hurd.
http://www.gnu.org

GNU General Public License (GPL)
One standard for licensing free software.
http://www.gnu.org/copyleft/gpl.html

Open Source Initiative
Dedicated to managing and promoting the Open Source trademark for the good of the community. Includes a definition of 'Open Source', and a list of approved licenses.
http://www.opensource.org/

Advogato
Community resource site for developers of free software; news, and diary service.
http://www.advogato.org/

Linux.org
Comprehensive information and resources about the Linux Operating System.
http://www.linux.org/