I had this working 'once' with GlobalScale and now it doesn't work. So I started from scratch. I have a MBP with Snow Leopard.
1) deleted the /System/Library/Extensions/FTDIUSBSerialDriver.kext. Rebooted.
2) Reinstalled the FTDI drivers from the FTDI website, using the 10.6 driver version.
3) Rebooted OSX
4) Copied the pre-made info.plist into the FTDIUSBSerialDriver.kext/Contents.
5) Ran sudo touch /System/Library/Extensions.
6) Plugged in GlobalScale plug.
7) Tried CoolTerm but no sign of USB device. Confirmed this w/ System Profiler.
Disconnect and power off Plugtop.
9) Reboot OSX.
10) Start CoolTerm.
11) Power on PlugTop.
12) No luck configuring CoolTerm w/ an active port.
Sheesh. It shouldn't be this difficult. Ideas?