I found it via http on some japanese rom site (they had the german and english versions). I only played the first level, but it's not as bad as the Oddworld Adventures, although the controls are kind of annoying (you have to be in the right spot to open spooce locks and it isn't really marked, for example).
Oh, and I'm sure I have a real copy of the game somewhere so I can legally download it...
And yes, VisualBoy Advance is a good emulator, so you can save games and not have to remember the level passcodes