Your right George its not available (not even on the Japanese or chinese stores) anymore. Lets hope it ll come back because its the most sophisticated midi app I could find at a reasonable price . I have it I could "share" it with you people but I dont know if it would work without the installer...
Otherwise "Midi PatchBay" and "old" application that still works fine under the latest OS version can do what is missing in the Qmidi. Just operate it again as a bridge between Qmidi and doc-850; You can mute or redirect midi channels, for instance send all data to channel 1 (useful for the disklavier) etc...