Lacking a satisfactory technical solution to handle article 6
of the LGPL, this license cannot be used for the Prolog source code that
is part of the SWI-Prolog system (both libraries and kernel code). This
situation is comparable to
libgcc, the runtime library used
with the GNU C compiler. Therefore, we use the same proven license terms
as this library. The libgcc license is the with a special exception.
Below we rephrase this exception adjusted to our needs:
As a special exception, if you link this library with other files, compiled with a Free Software compiler, 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.