But the instructions are quite right for an Ubuntu/Edgy desktop. The short, short steps are:
$ ssh homeserver -N -f -L 192.168.118.33:6689:localhost:3689
Instead of using the default 3689 port, pick a high number. First of all it means you won't have to start the ssh tunnel as root and it won't confuse banshee which wants to use that port itself. Also you need to specify your local ip address (eg: 192.168.118.33)
$ avahi-publish-address -v -H UbuntuLaptop.local -s "my personal homeserver tunes" _daap._tcp. 6689 &
Avahi is not Apple based code, so there is no mDNSProxyResponderPosix command. The above line is the equivalent to "mDNSProxyResponderPosix 127.0.0.1 squeal "shareName" _daap._tcp. 3689 &"
To debug this, keep an eye on /var/log/mt-daapd.log on the system running mt-daapd.
It appears that Rhythmbox gets a little confused about trying to connect to localhost:6689. Now only banshee dies when closing.