I'm used to launch two instances of mt-daapd (http://www.mt-daapd.org/)
service, to workaround a design limitation of that software (need all the
shared files to be on the same filesystem).
Launching two separate instances of mt-daapd (on different ports) in the same
machine works fine with the internal responder and when using a normal howl
responder, but it does not work when building against avahi with howl compat.
The HOWL API is broken when it comes to name conflicts. Please port mt-daapd to
our native API and your problems will go away.