"The manufacturers who are releasing USB MIDI interfaces are almost certainly creating their OMS drivers in native code, but they can't do much about the core of the program, which is now well past its sell-by date. As no-one has paid anything much for OMS for several years now, we cannot really complain that anyone is ripping us off. Of course, OMS's shortcomings mean that USB has acquired a reputation for being unreliable with MIDI, which I am not certain it deserves (or certainly has to share with OMS, at the very least)."
The rest is here: http://www.sospubs.co.uk/sos/feb01/articles/applenotes.htm
"Dozens of people spontaneously combust each year, it's just not that widely reported".