This is from the MM website:
Can I open Finale files (.mus or .musx) directly in Dorico?
Finale’s proprietary file format was specifically designed to be read only by Finale, making it difficult for other software to interpret. Much of the way a score is displayed in Finale depends on algorithms and routines unique to Finale’s code, which process the document when opened.
In contrast, MusicXML is designed for file exchange between different notation programs and is more suitable for this purpose. Steinberg is gathering tips and tricks to help ensure a smooth export/import process, which will be published on the Dorico blog soon. Since Dorico is actively being developed, MusicXML imports will likely continue to improve over time.
- Exporting MusicXML Files from Finale (Article)
- Import MusicXML into Dorico (Video)
Here is the full page:
Another reference: