http://translate.google.co.uk/translate?hl=en&sl=fr&u=http://www.console-techies.fr/&ei=kL-NSc33K-KJjAeWzeCuCg&sa=X&oi=translate&resnum=2&ct=result&prev=/search%3Fq%3DConsole-Techies%26hl%3Den%26sa%3DG multi region
So it's just a new version of the MultiBIOS using Mega CD 2 BIOS. From what I understand, the MultiMega uses a different type of chip and you'd probably break the thing in the process. It's four layers of PCB and there's really no room in there. You'd be better of with a Mega Cart from Tototek.
Uhh, where does it say this will work on a MultiMega? It's for a Mega CD (the new one being for Mega CD 2, NOT MultiMega). Why are people so determined to mod MultiMegas? If you have one, enjoy the fact that you have a fairly rare console and LEAVE IT ALONE! If you want to mod something, mod a much more common Mega Drive and Mega CD. You could sell your MultiMega and buy BOTH and still have change left over!!