The Klansman/Birth of a Nation

When we first see Burt Reynolds' character, he is performing on stage. The scene he is doing (wearing Klan robes on a fake horse with a fake sun behind him) is a reconstruction of the final shot in 'The Klansman' (later 'Birth of a Nation'), which Ryan O'Neal is watching at the end of 'Nickelodeon'. I seem to remember that 'The Klansman' was based on a novel - was it a stage-play before Griffiths made it into a movie, or is this scene just an in-joke?