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The GNU General Public License (GPL) is a pervasive Free and Open Source software license.

The GPL provides certain rights to anyone receiving a license to software governed by the GPL. At the same time, it imposes very few obligations except on those who wish to redistribute the software: Those rights and obligations are:

1. The right to copy and redistribute so long as you include a copyright notice and a disclaimer of warranties. You may charge for the cost of distribution and you may offer warranty protection for a fee.
2. The right to make derivative works for your own use.
3. The right to distribute derivative works so long as you:
   1. Identify the work as modified;
   2. License it under the GPL; and
   3. Provide the license information interactively if the program normally runs interactively.
   This section and the obligation to license under the GPL, does not apply to works which are independent works distributed with the GPL'd work and which run on the GPL'd works.
4. You may distribute the work only in executable form so long as the source code is:
   1. Distributed with the object code;
   2. Offered by a written offer, valid for a period of at least three years, to make the source code available for no more than the cost of distribution; and
   3. For non-commercial distributions, accompanied with the offer the redistributing party received as to the availability of the source code.
5. You may not impose restrictions on any of these rights.

For additional information and the full GNU General Public License, visit: http://www.gnu.org/licenses/gpl.html.