As this is a PHP script you'll need a working installation of PHP 4, it may work in PHP 5 but I have not tested it at all. You will also need the following:
Google Maps API Key, these keys are tied to a URL, so if you want more than one instanse of the map you'll need a few of these keys.
You should have PEAR::Config installed.
PEAR::Config is a seperate package from Pear, even if you have Pear installed you should still install PEAR::Config in addition to just Pear.
Included in the tar ball is a XML parser written by Eric Pollmann that was released under the Public Domain. This wrapper is known to work in PHP 4 only, there are some suggestions on making it work in PHP 5 at http://uk.php.net/manual/en/function.array-merge.php