Ask him to export his file as a MusicXML file (.xml), you could import it (via the File menu). Or install the Dolet plug-in, which imports MusicXML files as well..
Or get the free Notepad, or the demo of Finale 25 to open his file.
MacOsX 10.11.6, Finale 25.3, 2014.5, 2012c, Mac Mini Intel Core i7 2,7 Ghz, 16 Go Ram, Dolet 6. Azerty kb. Full TGTools. MOTU Midi Express XT USB, Roland Sound Canvas SC-88vl, MOTU Audio Express.