A little more info with a correction. According to the RFC (
http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt):
"The format of each constituent string within the DNS TXT record is a single length byte, followed by 0-255 bytes of text data."
So, the TXT record format I provided is not technically correct, and quotes are not necessary (just an artifact of tcpdump formatting). In mDNSResponder on FreeNAS, as audio
nvideo points out, there should be multiple lines. This will create the correct TXT record with length bytes. The more correct mdnsresponder.conf entry is
freenas
daap.tcp. local.
3689
txtvers=1
iTSh Version=131073
Version=196610
(Also note that there's a space between iTSh and Version, which somehow was removed earlier.) While I haven't needed additional key value pairs, iTunes does send out information for Password, Database ID, Machine Name, Machine ID, OSsi (not sure what this is), and Media Kinds Shared (35 from iTunes 8.1).
Avahi is probably similar, in that multiple txt-record entries should be used.