Well you could make a site like this with PHP, Javascript, CSS, and HTML sprinkled in then use MySQL for the databasing. As for what is used for this site, have no clue.
From what I gather, it uses HTML and CSS for markup, Javascript for form interaction and AJAX calls to cgi scripts, these cgi scripts might be written in c(++), perl, python, ... or even php if they have a custom extension configuration.
According to the server signature (if it is correct) it is hosted on a CentOS machine running Apache.