more.groupware is not your typical macupdate program. It is a collection of php scripts and database schemas, thus there is no installer and you cannot run it "out of the box".
You need a web-server with PHP, Apache and MySQL on it. Any modern Mac will have Apache but you have to download and configure PHP and MySQL yourself.
It is accessible through a web browser but only after you have set everything up and this is not easy to do (for someone who has never done it, anyway).
Bummer I know. However, maybe now is a good chance for you to explore your Mac a bit more and figure out how to do this. It's fun (well, for a geeky sort like me).