It's not possible to contact the developers of TREPCAD because their domain is expired. When you visit trepcad.com, a message is displayed on the middle of the page saying that the domain has been reserved and that's all about it.
I've also found the TREPCAD on another website. They appear to be resellers, and you can contact them to obtain additional info: http://www.graitec.com/ge/contact.asp
Note: German language might be necessary in order to communicate with them since they're a German-based website.