This MIDI file plays some notes on a drum channel, but that soundfont does not actually contain any drum kits. So if you import the DLS bank into OpenMPT's MIDI Library, it will keep using the GM.DLS drums or whatever soundfont was previously loaded.

From my understanding, SynthFont 1.730 is not behaving correctly either: As it cannot find a drum kit just like OpenMPT, it simply uses the first instrument (some metallic sound) as a replacement rather than actually using the instrument specified on that channel (patch 21, some kind of war drums). A YouTube recording of the track confirms my suspicion that SynthFont plays the file incorrectly as well.

For this to work at all in OpenMPT, its drum library would need to be entirely empty, and OpenMPT would need to fall back to loading melodic patches instead of drumkits if it cannot find any drumkits. However, I consider this MIDI file to be malformed and I am not going to make OpenMPT load a melodic instrument instead of a drumkit just because there are no drumkits in its library - that would be a very questionable hack for a single file. If you want the file to be played correctly in OpenMPT (and SynthFont and probably other players), you will have to insert a GS Drum Kit disable message for channel 10, or move its contents to a different MIDI channel.

• P.S. 1: It would be easier to just rename the DLS file to the same name as the MID file, then OpenMPT will use it directly and you don't have to replace the entire MIDI Library. It will not fix the problem, though.
• P.S. 2: OpenMPT is not a MIDI player.