Is this just for union members? Am I gonna have to join the union?

Short version: No and no. Although Fair Trade Music is sponsored by Local 99 and the American Federation of Musicians (AFM,) the musicians’ union, membership is not a requirement, either to participate or to benefit. So, the AFM is providing infrastructure and context to the campaign for the benefit of all musicians. It’s part of their mission, and we’re all in the same bathtub!