A MacOS emulator was already available for BeOS and able to run any MacOS 9 application on BeOS. If I remember correctly the code name was "sheep shaver"...
Yep, but it would only run up to 8.x. I think, 8.5, but it could have been 8.1. They Mac OS after 8.5 changed a lot, and I think the BeOS version of sheepshaver stopped being able to load the OS.
It worked with no extra files on a Mac running BeOS, on a BeBox it required a dump of the toolbox ROM.