It doesn’t look like much yet, but it looks like someone already started writing a DPAP server, and it looks to be open source, too!
http://search.cpan.org/~rclamp/Net-DPAP-Server-0.02/lib/Net/DPAP/Server.pm
I think it’s written in Perl? I’m no programmer, in fact I have trouble just writing shell scripts or batch files, but I’m sure someone else on this forum could expand on that script and make it work with albums and stuff.