Why don't you ask them? They have an email link on their help page
here[
^].
It could also be that they are using a custom, in house solution. The only way someone here would know this is if someone here happened to work on the build of that site which is why I suggest you ask them.
Typically, when sites are built using a pre-packaged CMS system, there would be a link to the site of the CMS developer somewhere on the page which there is not in this case.