I released Dumbo 0.21.26 the other day. As usual we fixed various bugs, but this release also incorporates an enhancement that makes it a bit more special, namely, some refactoring that can be regarded a first but important step towards plugable backends.
Dumbo currently has two different backends, one that runs locally on UNIX and another that runs on Hadoop Streaming. The code for both of these backends used to be interwoven with the core Dumbo logic, but now we abstracted it away behind a proper backend interface which will hopefully make it easier to add more backends in the future.
Personally, I would very much like Dumbo to get a backend for Avro Tether at some point. The two main starting points for making this happen would probably be my main refactoring commit and the Java implementation of a Tether client in the Avro unit tests.