This area of the law is not as strict as you might think. Consider the ribbon used in Sibelous (and many other programs), which clearly originated in Microsoft office. This pattern and visual style is a direct copy but not really worth arguing about, and likely difficult to prove specific damages against Microsoft even it they wanted to pursue it legally.
The big question is whether a program’s copying causes actual damages, this is where lawsuits come into play, when money is on the line. MuseScore’s interface borrowing elements from Dorico will be difficult to prove damages against Dorcio. The fact is, MuseScore is borrowing from many programs, and Dorcio is borrowing from many as well. Most products and works of art borrow heavily from existing products and works of art and the laws to distinguish direct copying are fairly specific and usually only matter when money is on the line (it can be proven that copying caused the original product to lose money).