libusb is compatible with OSX. I have used libusb+GridFlow+Pd on OSX to do some testing and it worked.
and if you read my email correctly, I said:
"change the Multio so that it also works as a non-HID device."
you quoted that line yourself.
Oh i'm so sorry, you are right. My fault. I deeply hope this won't happen again.
sincerely, Thomas