Do they already have a start at translation? A strings file associated w/ each map?
The strings are in the map html file in the form of a json object. You can see it at the very bottom if you view source. It would be possible to change this on the fly if an argument were passed to the url. We are already doing this in batch to cut down on the text displayed and add a popup.
But the OWID code is for me at least rather opaque in terms of implementing something directly in the app.