Not sure. I did not write the MMS script, just de-SDKed it, though I kind of doubted it would be compatible with BABS. It has been a while since I viewed the script, but I may take another look at it. I remember when I was messing with it, I saw a lot of room for improvement in the compatibility department. I noticed a lot of over-written methods, as opposed to aliasing them, etc., etc..
The main issue I could pretty much guarantee an issue with would be the ability to move with open windows, and a custom movement script together, which BABS comes with.