I've just opened my Xdebug repository on github. Importing my old SVN repository was a bit of a task. With the help of Ole Marius Smestad I managed to cook up a bash script to import and fix-up the repository. In the meanwhile I've learned more about git than I ever wanted to know, but still not enough. I maintain that, although git is very powerful, it is also a lot less intuitive than SVN (or even CVS).
In any case, Xdebug is now on github, as well as the Xdebug website (http://xdebug.org), my proof-of-concept debugging client GtkDBGp and the specification of the protocol that Xdebug uses: DBGp. The issue tracker is still at the old location—http://bugs.xdebug.org—and I am not intending to change that. I will keep the SVN repository active for now.