Non-English wikis use specific language keywords and messages. For example, French Wikipedia uses the word "REDIRECTION" instead of "REDIRECT" for redirect pages.
XOWA distributes all language files in the xowa_app_*.zip package. They can be found at /xowa/user/anonymous/lang/xowa/ under the appropriate language code. For example, the language definition for English is in en.gfs, French is fr.gfs, German is de.gfs, etc..