I cannot get that plugin to work. That page is how I would like it to work, effects not required though.
Ideally I'd like to have two textareas in the admin panel, one for each language's content. It seems like there isn't an extension that does this. Anyway, however you can get it to work like the above site is fine. I need this done ASAP!
Please specify how much you are willing to do this for. If things go well, I will return to you in the future for more wordpress fun, and possibly even invite you to one of our many non-wordpress programming projects :)