Since myth 1.0 (for the macintosh) only qwerty keyboards work as expected.
apparently myth is using a low level routine, and is mapping keycodes to ascii values using a hard coded table, instead of asking the system to do the conversion.
You are correct it is currently reading the raw key codes. I will give it some thought about what we want to do at this point in the game. Though since it's been in since 1.0, I'm afraid it's not going to be the highest of priorities.