Screenplay...
...by August Wilson, from his play. But as he died in 2005, this means that it was sitting for a decade before it was made. (From what I see, there are no other writing credits.) Truly a unique project.
P.S. And as I'm composing this post, I found this: "Playwright and screenwriter Tony Kushner came aboard to build on a draft written by Wilson before his death in 2005.[5] However, Wilson will be the only credited screenwriter for the film."