I'd be very surprised if it didn't run from an edrive. launching from non-writable volumes are the only place I've gotten grief from DW.
Oh one other requirement... DW requires that its application be launched from the booted drive. I have a service partition on my ext HD and I can't put dw on it because it MUST be launched from the booted drive. (not sure if this is an artificial limitation to do with their copy protection or what)
