Calendar Solution is a set of PHP classes, so, of course, you'll need PHP installed on your machine. It has to be at version 5.2 or later.
You will also need access to one of the following database systems:
While Calendar Solution is configured to run on Apache's HTTPD web server, it is possible to run it on other web servers by translating the .htaccess files to configuration files used by your web server. Examples of using Lighttpd are in the INSTALL.TXT file.