It is only the homepage which is down, the challenges are still accessible. I emailed Erik about it a few months ago, here's what he said.
"Dear Hul3man,
You can still access all the challenges (and the entire site, actually), e.g go here:
http://bright-shadows.net/hackchallenge.php
We hope to get the site back properly, but unfortunately lack the time to do so.
With apologies, thanks, and best wishes,
Erik"