You CAN open .tpl with Dreamweaver you just have to add them to your extensions list.
Here's how to do that:
Edit->Preferences(OR CTRL+U)->File Types/Editors
Theres a text box that says Open In Code View, you should have a list like this:
.js .asa .css .cs .config .inc .txt .as .asc .asr
just add .tpl to the end of that so it looks like this:
.js .asa .css .cs .config .inc .txt .as .asc .asr .tpl
And NogDog, for some reason or another dreamweaver doesn't check for file types, it only uses the extension. So if I had an mp3 and renamed it to song1.dwt(dreamweaver template) dw would still try to open it as a template. Its really weird