QGIS is currently (QGis 2.12) provided in about 40 languages, the setting can be changed in the Options. QGIS invites users to provide additional translations, which is not very difficult as it boils down to translate a list of words and short sentences. 



Besides the QGIS interface, the content of QRex reference tables can be translated as well from within QRex by filling the columns ‘label_lang’ and/or ‘comment_lang’ in each table from the ‘parameters’ layers’ group, and modifying the field widget setting accordingly as shown on the figure 2. The parameters tables can be edited if the user has the right privileges to do so.