Per the "Deploying a User Interface that Supports MLS" section in Chapter 14 ("Multiple Language Support") of the Oracle Configurator Implementation Guide:
"When a host application launches Oracle Configurator to configure an item, the language specified in the database ICX session ticket is passed to Oracle Configurator. Oracle Configurator uses this information to determine which translated text to retrieve from the database and display in the UI."
So essentially, Configurator will display the same language that the hosting application is displaying, the language the user has logged into EBS with. (Of course, translated text will only appear in Configurator if you have supplied translations in the CZ_LOCALIZED_TEXTS table.) If you need Configurator to display a different language than its hosting application, that would require a customization of the initialization string the hosting application sends to Configurator, specifying a different icx_session_ticket parameter value.
Hope this helps.