easy1600, from the way your output is, it looks like you're not in a bash shell, but just the su sh shell. exec the command bash then exec debdroid. Thank you for trying it out.
As for Gentoo, I've been using Debian for years and never messed about too much in other distros other than arch. Though if you can get an ARM Gentoo img this method can be tweaked to work with any ARM img really.
Update: Here's a WIP of the Debtop software which will allow basically the same functionality of the Motorola Atrix Webtop software.
This vnc session is all through USB with no interaction over the wlan though it has the ability to work with vnc over ssh tunnel.