It looks as though MuseScore will export XML, which Finale will import. Won’t that work for you?

Or is that what you mean by “html export”?

Just a curious question but if you were Finale would you make a direct import of a competitor's product? Even if it were possible? I am not sure I would.

Absolutely, yes. What a great feature:  “Finale can import directly from Sibelius, Dorico, MuseScore, and all other major notation programs!” Users would be able to use one notation product, but still handle the competition. Picture an octopus: Finale at the center, and all of the others out on the arms.

In theory, this is what MusicXML should do, but it still requires an extra step on the originator’s end. How many times have we gotten an original file from another program, and had to ask them to export as XML? As an example: Barbershop Harmony Society sent me a Sibelius file. I only have Sibelius First (the free version) so I couldn’t export XML. I could “print” to PDF,  although even that took some extra searching. I did that, and ran it through SmartScore, and then exported the XML, and imported it into Finale. A simple “Import Sibelius” would have save me a fair bit of time.

The file format of any program is proprietary, protected by copyright, so not really legal to just directly import unless there's a special agreement between the two companies.

Exactly! I don't see MM or Avid releasing the inner working of their software any time soon.

True. But that wasn't the question. I was responding to "should/would they, if it were possible?"