There are several stock Open Source Licenses, and variations of these licenses are used by different organizations.

GPL

• GNU Public License created and updated by the Free Software Foundation
• CopyLeft vs. Copyright
• Forces all distributed derivative works to be Open Source under GPL (often called viral licensing)

LGPL

• Lesser GPL, formerly Library GPL
• All alterations to the code itself must be released under the LGPL (bug fixes, new features, etc)
• Commonly used for libraries, all code linking to the code can be released under any license.

BSD Licenses

• Created by the University of California
• User is free to do whatever they want to do with code, and can redistribute the code under any license.
• Early Windows TCP/IP stack was a variation on BSD code
• Formerly had advertising clause which had to be put in source code comments.

Apache License

• Extension of the BSD License used by all products developed by the Apache Foundation
• Cannot use the Apache name, or advertise that the product uses Apache software without express permission