These are bzr branches. You can download them using the bzr branch command. If you open a branch in your browser, you will be forwarded to Loggerhead, a bzr web interface.
|bitlbee/||Main release/integration branch|
|contrib/||Personal branches from others|
|debian/||Debian packages (nightly builds of various branches)|
|tarballs/||Tarballs (with prebuilt docs) from bzr|
|lh/||Loggerhead, bzr viewer web interface|