For multiprocessing a log handler is needed that sends data to another process.
This might help: http://stackoverflow.com/questions/641420/how-should-i-log-while-using-multiprocessing-in-python
That is implemented now but the problem is that the interface is stupid. The ZeroMQ implementation is much more useful there and also provides a way to handle background threads.
Because the multi processing handler is using a multiprocessing queue it should probably be moved to the queues module and gain a similar interface to the ZeroMQ one. Maybe with a bit of magic that parent and child automatically select the correct side (handler / subscriber) which is usually not necessary for the ZeroMQ setup.
Fixed. They share a common baseclass now and a compatible interface.