I’ve never heard of “Prison Fellowship” sorry. I fail to see how complaints are made of “ with mandatory services, Bible study, and prayer for the participants” if they volunteered to be in the program?
Prison Fellowship is an international prison ministry organization founded by the late Chuck Colson, of Watergate fame.
Iirc, the complaint was that having a Christian program doing operations, as opposed to just visiting, in the prison was “establishment of religion.”