The theme from The Undiscovered Country was modified from Holst's Mars God of War and Neptune the Mystic, which are also in the public domain. Meyer wanted to use Holst as the soundtrack but the composer was forced to use original music because they were too expensive. However, the whole suite entered the Public Domain in 2004.
I bring this up SPECIFICALLY because I figure there's a chance Michael Henry or someone will be getting time with an orchestra soon for Neverwinter. I personally think getting recordings of Holst's music and maybe The Sky Boat Song would add a lot to the game if the devs have any orchestra time booked.