Not quite. The game can be just an exact copy of the original, that's run with some kind of emulation on the cube, OR it could be a port with enhanced features/graphics.
If you have some inside info on this matter, let me know, but all I know about the game, is that it's coming out on gamecube.
Edit: And sure it has to do with pj64. Isn't pj64 an emulator?