This software is copyright and you are explicitly granted a license which gives you, the "user" of the software, legal permission to copy, distribute and/or modify the software.
Note. This license applies to packages whose authors have not adopted the "Clarified" or 2.0 version of the Artistic license, and is not categorised as a free licence (and cannot therefore be included in TeX Live or other derived distributions).
Further information about this type of license is available from the Perl Web page and general information is available about other TeX Catalogue Licenses.