In an interview, the film’s creators explain how they skirted the copyright issues for the audio:

We had little to no budget for this project and we knew that the publishing house was going to be really skeptical of our little company’s request to utilize his work. We had faith in our vision for the video and that once it was complete they would see that this was something made with the best intentions in mind. We are in no way making any money directly from this video; it was purely a passion project. While we had high hopes for this, we could have never seen all of this attention coming. Sometimes it’s better to ask for forgiveness than permission.