I have patched the ebuild and init.d script to make mDNSResponder install the client program "dns-sd", and also the _other_ daemon - mDNSResponderPosix. mDNSResponderPosix is run in addition to mdnsd and allows you to register arbitrary services read from a config file - so you can add ssh/ftp/http entries etc for hosts on your network. Since I cannot seem to attach files to bugs, I have put the modified ebuild files up at http://lidskialf.net/mdnsd
Cf bug 96966
Fixed in mDNSResponder-107.1.