It is proposed that the document-link/language element can repeat to cater for documents that contain more than one language. This applies to both the Activity and Organisation standard.
(NB. that the use of the language element, rather than the xml:lang attribute, is deliberate - as it describes the language of the object, not the language being used in the xml)
For technical details about implementing this proposal go to: https://github.com/IATI/IATI-Schemas/issues/139