Authors don't have to create content in the same source language.
Each data cabinet in the repository is defined with a Language property or a language_locale string. Users can create content in a cabinet in the language specified for the cabinet. You can then translate that content into other target language cabinets. A cabinet can be both a target and a source cabinet, for purposes of translation workflow.
For example, most of your content is developed in English in a regular data cabinet, then translated into French and German target language cabinets. Composed output is delivered in English, French, and German. However, you may need to have some content developed in French in a French language cabinet. That content must then be translated into English and German target language cabinets for delivery.