Sorry, we no longer maintain the code repository website.

However the code itself, including archive of changes is available via our SVN repository: Can do a 'SVN Checkout', from this repository, to get the latest code, and access the historical changes.
svn checkout http://svn.geograph.org.uk/svn/trunk/ /path/to/geograph/
There is also a Roadmap to help find way around, as well as a basic Repository Viewer.