Well, a few Chrome specific features are used, but they're not required. For instance http://github.com/espruino/EspruinoOrion uses most of the IDE code, and works in most browsers.
It was definitely something I was looking at, and I don't think it should be too hard. If someone wanted to take it on it would be great though - it'd be really neat to have a self-contained executable IDE.
Just a thought have you tried running the IDE in NodeWebkit as a standalone IDE. Or are you using Chrome specific features that are not in NodeWebkit?