This work has been dedicated to the public domain by its creator, thus is free to use and reuse without restriction. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission. Attribution is recommended but not required.
Also see this detailed guide covering the copyright and ethical considerations of digital sampling of audio and video materials.
Why is this free to use?
Most music and recordings in the Free Music Archive are not in the public domain. However, Citizen DJ provides a subset of recordings from the Free Music Archive that were published under a Public domain dedication license by their creators, thus are in the public domain.