ServiceDesk (7.1) and Workflow (7.1 MP1) have been internationalized to an extent. The installer and portal portions of the product have been translated to German (plus 9 other languages)
you can flip the ServiceDesk/Workflow ProcessManager portal to use German by specifying German as the primary language in your browser.
In Firefox: Tools - Options... Content tab... Languages section Choose button (add German to be the preferred language)
In IE: Tools - Internet Options... General tab... Languages button (add German to be the preferred language)
Other portions of the product (client tools, designer tool) are being slated for internationalization in future releases.