As an experiment I installed mojoPortal on my Windows Home Server 1.0 box a year or so ago, and it worked great. I was flirting with the idea of opening it to the Internet but decided against it. We are running our production mojoPortal installation on Server 2008 R2 (64-bit). Since WHS 2011 is based on Server 2008 R2, I'm almost positive you'll be able to get mojoPortal running on it pretty easily.
Jamie