Corigliano- altered states ends up in his first symphony
There's a bit of his clarinet concerto in Altered States, and a bit of Altered States in the Pied Piper Fantasy, but I hear nothing of that score in the First Symphony. The symphony does however make use of the entire battle cue from Revolution.
Plagiarism is passing off the work of someone else as one's own.
Using your own music -- music that you wrote and that you OWN authorship of -- is yours to do with as you please.
Getting all het up over Korngold using his film themes in his concert works is inconsequential histrionics.
Get over it.
And often the material from movie scores is expanded upon and re-worked for concert pieces in a way that allows creativity and development that can't be done in scores because of the timing to picture issues.