The
GNU Free Documentation License (
GNU FDL or simply
GFDL) is a
copyleft license for free documentation, designed by the
Free Software Foundation (FSF) for the
GNU Project. It is similar to the
GNU General Public License, giving readers the rights to copy, redistribute, and modify a work and requires all copies and derivatives to be available under the same license. Copies may also be sold commercially, but, if produced in larger quantities (greater than 100), the original document or source code must be made available to the work's recipient.