Add a Changelog (best named 'Changes') to the distribution. It should list at least major changes implemented in newer versions.
Add a section called "LICENSE" to the documentation, or add a file named LICENSE to the distribution.
Add =head1 LICENSE and the text of the license to the main module in your code.
Add =head1 LICENSE and/or the proper text of the well-known license to the main module in your code.
This is not a critical issue. Currently mainly informative for the CPANTS authors. It might be removed later.