The Star Wars Anthology musical collection did not borrow its style too closely to prior musical works. Some people believe the music somewhat resembles another piece that was already out, but the melody does not much close enough. It is very hard for a person to prosecute for committing plagiarism in today's society.
I do not believe the Star Wars anthology musical collection borrows it styles and melodies too closely from prior musical works and compositions. It should not be considered plagiarism. This is the first time I have ever heard anyone insinuate this problem and quite frankly I find it to be unfounded.
All music is inspired in some way by music that has come before it. As much as we like to pretend that music has infinite possibilities, it doesn't. Mathematically speaking, there are only so many combinations of notes allowed in 16 bars. Eventually the same one will have to be used twice.
No, the Star Wars anthology collection does not borrow its musical styles too closely from prior musical works, because there are no specific compilations that it is said to be copying. John William's body of compositions is so vast and so diverse, no serious argument can be made that he is not to credit for the work.
I personally think that the Star Wars anthology musical collection borrowed its styles and melodies too closely but did not considered plagiarism. I personally think that the Star War just considered taking a little bit of their style because they liked but they turned around and did a little twist with it.