Basically languages would be added according to demand. So far, other than English we only support Spanish since it is the one we found to be the most requested. We expect to add more languages as demand for them increases.
On the other hand, for the project interface the app already supports virtually any language and string encoding, so you should be able to use this feature to configure the app for your needs. For users without administrator privileges the chances of finding texts in English on the part of the app they are using is quite limited and we believe that such texts are easy to understand.