Neither MOS or OS4 will work on a Mac. OS4 will not work on Pegasos, and MOS will not work on AmigaONE. These things you can be sure of, unless there is a titanic change in direction.
As for Linux and BSD, most distros will run on A1, Pegasos and Mac. However, no kernels are adapted for Articia 'features' so on A1 you'll have to disable IDE UDMA - making Linux *very* slow. You can also run MacOS on MOL on either A1 or Pegasos.
Pegasos is designed and marketed to run as many OS's as possible. AmigaONE is targetted only at OS4 at the moment, and considerably more expensive.
Edit: boo, Red got there first. ;-)
