Yes "At Court" is actually by Mozart:
http://www.youtube.com/watch?v=XOuv-e2X7vo
If you keep listening you can hear they used bits out of different variations. "At Court" is quite a nice arrangement IMO
"Spirit" is based on the same idea but varied quite a bit. I can play both on Piano.
I've heard it in some movie based in (18th/19th century England I think) at a dance (I was a lot younger, I don't remember the movie I just remember shouting out "It's Knights and Merchants!" much to my family's confusion and bemusement
Also when I show KaM to a few people they're like "this music sounds really familiar" and I explain to them.
Also when I was first learning piano my teacher gave my a simplified version of that Mozart theme, and then he was very surprised when I came back next week and played the much more elaborate and complicated "At Court" because that's how my ear wanted it to go
I don't know of any other KaM tracks that come from somewhere else, but maybe some do
You can find the sheet music of some of the KaM songs (transposed by me) on my KaM music page that I made years ago:
http://lewin.hodgman.id.au/kam/index.ph ... itor_music