Correct. Everything done right, nothing related to Tremulous or GTKRadiant installed twice.
As for errors, there aren't any in my understanding, its just that I followed the steps at that site and got nothing, as in, no "Tremulous" on the drop-down menu, and I tried to open the Tremulous maps with every option possible and couldn't open them. Tell me what to look for and I'll find it, if you can.