When DisplayFusion is in beta, we're usually adding or changing text in the UI, so the language files from older versions are incomplete.
However, starting with 3.5 Beta 2, we've made it so that incomplete language files can still be used, and any strings that are untranslated will just appear in English.
Please send me an email at support@displayfusion.com and let me know what language you need, and I'll send over the most up-to-date version.