Did Trumbo work as a political censor?

When the King Brothers and Trumbo begin to expand their activity and bring in other, blacklisted writers, Trumbo agrees to provide them with as many re-writes as necessary. In one scene, Trumbo is shown re-writing another communist's script and editing out themes that dramatized communism. That activity, if done by a government employee, would amount to government censorship. Done by Trumbo, it was not.

The King Brothers had a valid interest in requiring sanitation of the scripts by Trumbo. They wanted successful films, but they didn't want to be accused of advancing communism. And they had no clue as to which ideas were considered communistic. You can also see in the scene where Trumbo cuts the communism from a script, the original script writer's only resource for story development is his repository of communist propaganda.

Note that Trumbo's screenplay that broke the Hollywood blacklist was Spartacus. Spartacus is a film about an individual who led a slave rebellion against the Roman Empire. Individualism is a bedrock theme of capitalistic propaganda. It is the antithesis of collectivism.

You might also see that throughout "Trumbo," the blacklist wasn't really about opposition to communism in America. It was about opposition to the cold war's red scare, the cold war having begun with the failure of American-Soviet talks to achieve a unified, democratic Korea in 1946-7.

Soviet Communism was an aggressive, revolutionary ideology, and the Soviets sought to direct all communist political movements worldwide. They were especially tough on communist parties in Eastern Europe, dictating to them without consultation or input.

You don't have to accept that every communist in America was a Soviet spy or even a willing Soviet spy, but it is mainstream, accepted history that Soviet Communists would use every resource they could to expand their ideological empire, including useful idiots.

And in the opening, Trumbo's daughter fails the communism test. She says she'd share her lunch, a voluntary act of generosity. She acknowledges her property right in her own lunch ("ham and cheese"), and then gives to another in need. Had she said the solution was to demand that someone else provide the hungry child with a free lunch, then she'd be a communist. Communism is about forcing someone else to pick up the tab, and taking credit for it.