The only chance I think you'd have is to find a KVM that uses USB, because that's the only way apples connect.
maybe you could try using USB->PS/2 convertors on the Macs stuff - but don't come crying to me if it doesn't work. & not only that, but how are you gonna hook up ANYTHING to the Mac ?? I mean it has 2 USB ports - if you've got cables from there to a KVM (1 for mouse/1 for keyboard) you can't use a scanner/printer/ANYTHING.
Cuz there are 2 extra ports on the keyboard
Oh yea - all this is just my senseless ideas re: my gf's G4 - I really dunno much about older Macs