The source code for the tdtd Emacs code for DTDs is now available for checkout from https://svn.menteith.com/trunk/tdtd and for browsing from http://www.menteith.com/browser/trunk/tdtd.
I didn’t think it would happen straight after setting up the Trac, but I’d wanted to use tdtd on a new (virtual) PC, and it was preferable to put the code into the repository and check it out onto the new PC than to scp a copy onto the new PC and risk the copy becoming out of sync w.r.t. the other copies floating around on my computers. Of course, now those other copies have to be updated to use the Subversion version instead of either the RCS or the Ubuntu versions.
The website and repository for tdtd are provided by Menteith Consulting Ltd.