You simply download it from:
http://www.minivend.com/minivend/download.html
You also need Perl 5.005 or higher, available from CPAN. 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. See the GPL at:
http://www.gnu.org/copyleft/gpl.txt