there is a translatewiki page, but there are some things missing for localization. specifically, the legends for rows and files, the pieces, and possibly a way to modify the notation - i think standard notation in hebrew uses colon instead of x to mark capture, for instance. in the standalone this is done by providing a "substitution table", so we replace "Q" with מה, while other wikis replace it with the unicode queen symbol (for this, the substitution can discriminate, and use different substitutions depending on skin color).
tl;dr: it's not enough to translate messages - row and file legends should be i18n-ed too, as well as piece symbols.
peace