My suggestion would be to run a whois report on the domain name: http://www.register.com/whois.rcmx .  That will give you any contact information that they made public when registering the site.  For this particular group, an actual phone number is included ;)  Best of luck.

Bummer.  I just bought some stuff from the guy about 6 months ago.  Dan was really responsive to support questions at the time.  Judging by recent reviews on snowcovered, it appears that other buyers are now having the same issue as you. 

It would be a shame if this guy bailed on his software without at least notifying customers or removing his products from the snowcovered marketplace.  That looks bad for Snowcovered and DotNetNuke as well.