I was hearing more and more positive things about Git and GitHub from my peers. So I took the PHP_ObjectFreezer code base and migrated it to Git and hosted the repository and GitHub to experiment with both the tool and the platform. It was a step that I did not regret and all the projects that I started since then are hosted on GitHub: bytekit-cli, phpcpd, phpdcd, phploc, PHP_CodeCoverage, PHP_FileIterator, PHP_ObjectFreezer, Text_Template, PHP_TokenStream.
He explains some of his thinking behind the move and why he moved towards a distributed version control model rather than something like subversion. So, if you're looking for the latest sources for PHPUnit, you'll find them here. (He also includes the steps he took to import the code into github by making use of the svn2git tool).