Didn't work.
I extracted the kext, copied it to the S/L/E folder, changed persmissions and ownership, deleted the S/L/Extensions.mkext or whatever, and it didnt work.
I restored from time machine, ran the areca installer, it exited abruptly (although still leaving behind the kext). I then downloaded and installed the full combo updater from Apple, rebooted, and it failed.
Did I need to reboot after the areca installer and before the updater?
This is really depressing =(