From LimeSurvey Manual
More languages can be added to your survey. This option is important when you want to create multilingual surveys. For example, if you wish to use English, German, and Romanian for your survey, add Romanian and German as additional languages (if English is already the default/base language). The list of available languages could be smaller if the LimeSurvey administrator diminished the number of available languages from the LimeSurvey global settings.