Almost all files declares: This package and its accompanying libraries is free software; you can redistribute it and/or modify it under the terms of the GPL (either version 1, or at your option, any later version) or the Artistic License 2.0. Refer to LICENSE for the full license text. In addition, please see DISCLAIMER.txt for disclaimers of warranty. That means (GPL+ or Artistic 2.0). LICENSE starts with text: a) the GNU General Public License as published by the Free Software Foundation; either version 1, or (at your option) any later version, or b) the "Artistic License 2.0" which means also (GPL+ or Artistic 2.0), but then it quotes GPLv2 and Artistic 2.0 what can be understood (GPLv2+ or Artistic 2.0). Finally, DISCLAIMER.txt reads: This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See the Artistic License file in the main Perl distribution for specific terms and conditions of use. However this means (GPL+ or Artistic) because Perl does not use Artistic 2.0 license <>. I believe you thought (GPL+ or Artistic 2.0) but it would be great if you clarified your intention. For example by replacing the GPLv2 quotation with GPL 1 in the LICENSE file and by changing the DISCLAIMER.txt file not to point to Perl's license.