rdup version 0.9.1 has just been released. I'm hoping this is the last release before 1.0.0. A bug in rdup's -c output has been fixed.

See the project page for more information or just download the damn thing right away. It's sha1 sum is 2f32cc18c1c58666443d0c3456b97d5c61376511 in case you care.