From my tests, the Atari ST TOS replacement "EmuTOS" (in an ST emulator) will not yet run STOS, François' ST-based precursor to AMOS. (It emulates with a real TOS/ST ROM.)
In that respect, AROS-68k has the edge, we have 100% free (cross-platform emulated) AMOSPro already.
P.S. One of the relevant developers has posted on my Facebook wall: