copyleft: /kop'ee-left/ [play on `copyright'] n. 1. The copyright notice (`General Public License') carried by GNU EMACS and other Free Software Foundation software, granting reuse and reproduction rights to all comers (but see also General Public Virus). 2. By extension, any copyright notice intended to achieve similar aims. http://www.tuxedo.org/~esr/jargon/html/entry/copyleft.html
“All knowledge all discoveries belong to everybody. … All knowledge all discoveries belong to you by right. It is time to demand what belongs to you.” – William S. Burroughs, The Job
The GNU General Public License, or GNU GPL for short. http://www.fsf.org/licenses/gpl.html This is a free software license, and a copyleft license. We recommend it for most software packages.
The Clarified Artistic License http://www.statistica.unimib.it/utenti/dellavedova/software/artistic2.html This license is a free software license, compatible with the GPL. It is the minimal set of changes needed to correct the vagueness of the Original Artistic License.
The GNU Free Documentation License http://www.fsf.org/copyleft/fdl.html This is a license intended for use on copylefted free documentation. We plan to adopt it for all GNU manuals.
The FreeBSD Documentation License http://www.FreeBSD.org/doc/en_US.ISO8859-1/books/handbook/ln15.html This is a permissive non-copyleft Free Documentation license that is compatible with the GNU FDL.
The Design Science License http://dsl.org/copyleft/dsl.txt This is a free and copyleft license meant for general data, not particularly for software.
Note, though, that the GNU GPL can be used for general data which is not software, as long as one can determine what the definition of “source code” refers to in the particular case. As it turns out, the DSL also requires that you determine what the “source code” is, using approximately the same definition that the GPL uses.
mindguard public license for memetic protection http://zapatopi.net/mgpl.html