I probably should have mentioned the purpose of my request.

I am hoping to get to the point where I can make changes to the OS (bug fixes, improvements, new features, etc). I was hoping I could license the source code or get Roland to make it available to the community but they are very strict about their intellectual property.
In addition to the older firmware, I'm looking for a working MV-8800. All it really needs to be able to do is boot and work on a VGA display. It can have issues, etc. Need one for doing testing on that isn't my main machine in the event I end up bricking it testing changes out (at least until I figure out how to blast flash manually).