These spams don't actually come from this domain. You can prove this by checking the headers of the spam email. True dontworry.org emails come from the registered IP address:
65.75.163.220
Spam emails will say something like:
Received: from unknown (HELO dontworry.org) (81.195.197.30)
The IP address 81.195.197.30 is where this spam really came from. (In all likelyhood,
this is from a home computer that has been hijacked by a nasty virus.)
Mail from dontworry.org will display the IP address 65.75.163.220 clearly in the header.
I sincerely regret any inconvenience these spammers have caused you. I'm looking into what legal actions I can take to mitigate the damages they have caused.