With OJS, you can upload multiple galley files for final publication. This can certainly be several translated versions of an article. You can indicate what language each version is in the file label field when uploading. However, I don't believe there is a way to set the "language" field for the metadata unless that language is enabled in some way on the journal.
When enabling languages, you can choose to have the languages available in the User Interface, Submissions, or Forms. If you only enabled the languages for Forms, you should be able to select that language for the file's descriptive metadata but not have the language available for the interface.
Electronic Publications Manager
Office of Scholarly Communication and Publishing
University Library System, University of Pittsburghvgabler@pitt.edu