forked-daapd is a free iTunes server, and diegocaro describes a forward port to Raspbian here, which he recommends instead of the foorked-daapd normally packaged with Raspbian Wheezy due to problems with the libevent-2.0 dependency. His port uses libevent-1.4.1. I followed his description, and lo and behold, it works, i.e. I can see my music on a iTunes client. Well, it almost worked. I did get drops.
I experimented with the iTunes setting in /etc/forked-daapd.conf
# Should iTunes metadata override ours?
itunes_overrides = true
I upped the log level in the conf file and looked at the log output with
tail -f /var/log/forked-daapd.log
and saw that I started to process the 'iTunes Music Library.xml' file, whose entries refer to the old mp3 file locations back from when I still had the music HD directly on my Windows box, resulting in a slew of "Could not find..." messages. Now the iTunes client is still seeing the share, but hangs at Loading and then reverts back to the local library. So I turned the commented out itunes override again.