Conversation so far:
What was Vidal's first screenplay?
In 1958, the director William Wyler required a script doctor to rewrite the screenplay for Ben-Hur (1959).
How did Vidal become involved in Ben-Hur?
Vidal rewrote portions of the script to resolve ambiguities of character motivation.
Was his work on Ben-Hur successful for him?
In exchange for rewriting the Ben-Hur screenplay, on location in Italy, Vidal negotiated the early termination (at the two-year mark) of his four-year contract with MGM.
Where did he go after that?
Vidal occasionally returned to the movie business, and wrote historically accurate teleplays and screenplays about subjects important to him.
Were any of those screenplays notable?
Two such movies are the cowboy movie Billy the Kid (1989).
and the other movie?
the Roman Empire movie Caligula (1979), from which Vidal had his screenwriter credit removed.
why did he have his credit removed?
the producer, Bob Guccione, the director, Tinto Brass and the leading actor, Malcolm McDowell, rewrote the script.
Did that cause conflict for him?
added extra sex and violence to increase the commercial success of a movie based upon the life of the Roman Emperor Caligula (AD 12-41).
What did he do after those films?
CANNOTANSWER.
Are there any other interesting aspects about this article?
the documentary film The Celluloid Closet (1995).

Question: is there any information about his work on that film?
Self-contained rewrite: Is there any information about Gore Vidal's work on that The Celluloid Closet (1995)?