thing:And yes, you can save a file that a non-Passport user can open - you just have to make sure you save it as a single-language file.
Which is true for QuarkXPress 3, 4, 5 and 6.
From version 7 onwards the file format is the same, so the US and IE version of QuarkXPress can open files saved in QuarkXPress Passport.
Best
Matthias