Looked at the screenshot, is this using some sort of integration with Screenhero? After playing/using Screenhero, I've been excited about the possibility of incorporating it into web apps.
Guess you could set up XP in a VirtualBox specifically for this purpose.
I know Teamviewer is compatible with Linux (They use a pre-configured WINE/Mono type build, alike Picasa for Linux). Used it myself and it works as well as the native thing on both ends.