I was able to get it to work. I navigated to the GdbDomainTools.dll (..\src\GdbDomainTools\bin\Release), right clicked on the file and clicked register. It poped up a dialog asking which product I wanted to register it for (Choose desktop). I then closed and reopened ArcCatalog and the additional tab showed up on the Database Properties window....it still seems to work at 10.0. This tools is great!