swipl

Indicates this module is distributed under the GNU General Public License (GPL) with the SWI-Prolog exception:^{130This exception is a straight re-phrasing of the license used for libgcc, the GNU C runtime library facing similar technical issues.}

As a special exception, if you link this library with other files, compiled with SWI-Prolog, to produce an executable, this library does not by itself cause the resulting executable to be covered by the GNU General Public License. This exception does not, however, invalidate any other reasons why the executable file might be covered by the GNU General Public License.

This should be the default for software contributed to the SWI-Prolog project as it allows the community to prosper both in the free and non-free world. Still, people using SWI-Prolog to create non-free applications must contribute sources to improvements they make to the community.

lgpl

This is the default license for foreign libraries linked with SWI-Prolog. Use PL_license() to register the condition from foreign code.

gpl

Indicates this module is strictly Free Software, which implies it cannot be used together with any module that is incompatible with the GPL. Please only use these conditions when forced by other code used in the component.

Other licenses known to the system are guile, gnu_ada, x11, expat, sml, public_domain, cryptix, bsd, zlib, lgpl_compatible and gpl_compatible. New licenses can be defined by adding clauses for the multifile predicate license:license/3. Below is an example. The second argument is either gpl or lgpl to indicate compatibility with these licenses. Other values cause the license to be interpreted as proprietary. Proprietary licenses are reported by eval_license/0. See the file boot/license.pl for details.

:- multifile license:license/3.

license:license(mylicense, lgpl,
                [ comment('My personal license'),
                  url('http://www.mine.org/license.html')
                ]).

:- license(mylicense).