Hey fox-didl,
The widget actually includes German translation text for when your WordPress site is set up to use German according to this site: http://codex.wordpress.org/Installing_WordPress_in_Your_Language
The only remaining text beyond system text and error messages which would need further elaboration would be the need to update your field titles themselves within MailChimp. If you head in MailChimp to Lists > your list > List fields and *|MERGE|* tags, you can change the names of the fields to be in German instead of English, then refresh your plugin’s settings within WordPress to carry over the updated titles.
If we can help with anything else, please let us know.
-Gabe
