[1] Frequently Asked Questions about the GNU Licenses - GNU Project - Free Software Foundation (FSF) (2009-09-09 08:01:07 +09:00 版) http://www.gnu.org/licenses/gpl-faq.html#InterpreterIncompat

[2] Frequently Asked Questions about the GNU Licenses - GNU Project - Free Software Foundation (FSF) (2009-09-09 08:01:07 +09:00 版) http://www.gnu.org/licenses/gpl-faq.html#WMS

[3] Perl Licensing - perl.org (2009-09-09 08:22:56 +09:00 版) http://dev.perl.org/licenses/