Email ATDN, Global Crossing, Cogent Communications, and many of the other companies they peer with and say the website has not been shut down despite emails sent to Softlayer. Those companies may threaten to nullroute the website's IP.
If they don't do anything (unlikely) get an injunction.
It's trivial for this guy to get it hosted elsewhere, however. This is just me, but I wouldn't expect to build anything in HTML5 that couldn't be copied-- the platform is inherently open. If the only creative and useful properties of your work is built in the open, there does not seem to be a compelling reason why you would be protected by copyright. This person could build a website around your "copyrights" in little time.