You simply download it from:
http://www.minivend.com/minivend/download.html
It also sometimes appears in the Comprehensive Perl Archive Network (CPAN) library. There are over 40 CPAN sites worldwide. The master site is ftp.funet.fi, with mirror sites located on every continent except Antarctica. MiniVend is available in the directory:
CPAN/authors/id/MIKEH
where CPAN is the base URL for any CPAN site. A list of CPAN locations is always available at
http://www.perl.com/CPAN/
As to cost, MiniVend is free within the confines of the GNU General Public License. Basically, any individual or company can use MiniVend free of charge -- you have certain responsibilities if you modify your copy then redistribute it.