The good news is that I just submitted a pull request (#863) for a minimal i18n support (and updated the issue #502).
The bad news is that I tested without errors when inserting gettext commands in layout.utml but does not work when doing the same in other templates (e.g. main.utml). I get "Undefined command gettext" when rendering the page :(
I suppose the problem is that I put the JS code in the wrong place.
So I'm stuck here. I hope other people can continue this work or guide me a bit...