Dan,.. I'm pretty sure she shutdown the site/company... although I want to believe she had a email to reach her? (yeah, great little tool!)
..here was a thread on the subject...
Further development of Propogator was stopped long back and Brenda was looking to sell out the program/site to someone who may be interested in developing it further. So yes, the site is no longer functional.
You may try #TASK tool which is free to use.
I used to know "CustomSolids" founder/programmer pretty well. I think she abandoned it some time ago.