For an overview of how this site came to run on DotNetNuke, after running on CommunityServer for a few years read this blog post.
This website runs on the latest version of DotNetNuke Community Edition 4.9.2, and the Engage: Publish module from www.engagesoftware.com. For URL cleanup I use URL Master from Ifinity.
For a few years the site ran on variations of the CommunityServer platform but due to the platform's licensing changes I decided to convert from CommunityServer to DotNetNuke.
The fact that I am a DotNetNuke Core Team Member also had a little to do with that as well.