Joubere stock does contain salt (0.2 g sodium per 100g). Lowest salt stock I have found is Kallo low salt vegetable stock cubes (0.03g sodium per 100ml of stock). I get them from the local health food shop.
You should also check whether they have MSG (monosodium glutamate) which is a flavor enhancer that doesn't agree with lots of people (give me blurry vision and headaches). I think Kallo is one of the only brands that doesn't have it.