Freeman had been in poor health since heart surgery in March and died last Friday, The Los Angeles Times reported.
Freeman helped establish the Screen Writers Guild, reorganized it into the Writers Guild of America in 1954 and negotiated with studios for the guild's right to determine film writing credits, the Times said.
During World War II, Freeman co-founded the Navy unit of Armed Forces Radio, where he wrote training films and entertainment for the troops.
After finishing his military service, Freeman wrote for radio's "The Baby Snooks Show" starring Fanny Brice. His film work included the talking mule movies, "Francis Joins the WACs" and "Francis in the Navy."
Freeman wrote for TV shows such as "Playhouse 90" and "The Loretta Young Show" and created the western "Sugarfoot."
Freeman is survived by sons Seth and Jonathan, and one granddaughter.