I've heard a slightly different story about the film's gay subtext, although probably no one living today knows the truth. I remember reading somewhere that it was Stephen Boyd's idea. He had read Wallace's novel, seen the '25 original, was convinced Messala was gay, and approached Wyler about it. When the two boyhood friends are reunited in the Roman barracks, Judah greets Messala enthusiastically but without any underlying subtext while Messala looks at Judah with longing and passion and says softly "I said I'd come back."
Messala tells Judah that he has been sent to Jerusalem to keep the peace. He wants Judah to become an informant against rebellious Jews, provide him with their names, and thus become a patriot in the eyes of Rome. Judah bitterly refuses, proclaiming that he can not be a traitor to his own people. That decision is what initiates their feud.
After Messala sends Judah to the galleys and Miriam and Tirzah to the dungeon, it is sort of hinted that Drusus will be his sexual partner.
Both the Boyd and Vidal stories are plausible. However, there is no doubt that the film as a very definite gay subtext.