themes.gallery2.hu theme demo -- module or custom code?

I would like to offer the visitors to our parish gallery the option to select which theme they would like to use. I was searching on the http://gallery.menalto.com/forum and there was a link to the http://themes.gallery2.hu theme demo site. The ability to select which theme to use (as on the top of the http://themes.gallery2.hu demo site) is exactly what I was hoping to offer. Is that custom code or a module/addon? Is it available?

I emailed the admin of http://themes.gallery2.hu using the address on the footer, but I thought that I would try here just in case someone else had an answer/insight.

Thanks.