I don't know if it was intended as a dongle, or if an updated GAL was required to fix bugs (either is possible with good ol' Jim Drew). Regardless, I've never seen 586 emulation working on the Emplant.
One with the correct chip was on eBay a year or two ago and, annoyingly, I think it has the exact same markings as the original chip.
Did anyone here end up with that board?