"[Burnett] would send scripts our way and ask doctrinal or Bible questions about it, but a lot of it was a friendship and an advisory role," Osteen said.
Osteen said much of his work was confirming if the extrabiblical material stayed true to the Bible.
His encouragement to Burnett was to "use your creativity to fill in between the lines."
Another consultant was Rabbi Joshua Garroway, an assistant professor at the Hebrew Union College and an expert on early Christianity and the Second Jewish commonwealth (circa 530 B.C. to 70 A.D.) Judaism. He was a paid consultant on the project.
"One of the issues that came up frequently in the comments was the goal of the production was to remain faithful, or at least as faithful as possible, to the narrative and text of the Bible, as opposed to a historical critical approach," he said.
"The series is not meant to be a historical feature but as a representation of the biblical narrative which is at times historical and at times not," Garroway said.
One reason Garroway thought he was brought in was because in parts of the New Testament, "there are less than generous depictions of Jews, Jewish leaders and Jewish traditions."
One of several Jewish scholars involved, his role as a New Testament scholar was to help the production stay faithful to the text but also "diminish as much as possible scenes or statements that could be construed as overly negative toward Jews and Jewish judgment."
While he thinks the project has an overall Christian orientation, "I think they did well."
"I don't think it will run into the same problems that Mel Gibson's movie ("The Passion of the Christ") did because the producers have been somewhat conscientious about forestalling some of the things that could produce that effect in the Jewish community," he said, referring to perceptions of anti-Semitism from the 2004 film.
Osteen thinks the project will have a lasting impact in churches. He plans to use pieces of the project in his services to help illustrate points he'll make in his sermons.
"I know I'm biased because I'm their friend, but I think it'll be something that will live on for generations because it's done with excellence, not knocking anything else, it's just this is production 50 years past where some of the other films were made," he said.
Burnett and Downey also think this project will be their most lasting and most viewed.
Burnett said the couple have deferred all their fees for the project. They probably don't need the money anyway. Forbes lists Burnett as among its 100 highest-earning celebrities with an estimated income of $55 million in 2012.
While the History Channel owns the exclusive North American rights to the project, Burnett and Downey own the rights to global distribution and theatrical airings, which are in the works. There is also a book tie-in, games and apps attached to the project.
For the couple, the project was not about turning a profit, though they likely will. Instead, it was about bringing new life to the stories of their faith for a new audience.
"Will it be screened in movie theaters? Yes, for sure. "Already been approached. Arenas, churches, every way you can imagine," Burnett said.
Burnett ticked through the shows he and Downey have put together over the years. "Over the next 25 years," he said, "more people will see this than all the others combined."