Has anyone ever been able to find an actual score to Powell's "Forbidden Friendship" from How to Train your Dragon? The closest I have been able to find was from a website called Musescore.com.

What do you mean by "score"? The "score" is all the music written/recorded for the film.
Are you referring to the sheets?

Yes, I mean the sheets for it.

I know this guy (http://forums.ffshrine.org/member.php?u=705303) once shared the (almost) complete sheets of How To Train Your Dragon, but unfortunately "Forbidden Friendship" is one of the few missing sheets :/ But if you're interested in other sheets from the movie, you can ask him.