A project student has the task of developing useful 7DS-like applications on our lab's Nokia n800, so we went searching for how to develop applications on this platform.
It appears that Python is the Nokia n800's programming language of choice - tough luck for Java. So we would have to start working with Python and developing our framework in that language.
In order to use Bonjour on Python for the Nokia, we need the pyBonjour library.
We also need to install the Bonjour mDNSd daemon for handling mDNS packets - or Avahi, which is more supported on Linux. A look around reveals that Avahi is available on the Nokia n800 through the Canola project.
But for pyBonjour to work with Avahi, the binary-compatibility layer with Bonjour need to be installed [libdnssd1 and libdnssd-dev].
There are existing demo applications (one and two) on Nokia using Bonjour. Both seem to relate to web servers.
Some more info about Python and mDNS from razorvine.