I didn't see this when you first posted it. This mod has hard-coded English text in parts, and will need to have more text constants created to allow it to be multilingual.

Search in Tools > Developers Toolkit for BOX_SHOPPING_CART_EMPTY to find the file where some text is correctly defined; other defines can be added there.

The Shoppingcart/Freeship in Header mod has done those define tasks already, and it may serve as a guide for you. It is not yet active in Free Addons, but you can get the zip from the support thread.