They simply have obtained rights from Bob to reproduce and sell the tapes. I have noted that Joyner often speaks for Jones on many occasions, and 'interprets' prophecies for him too. He has sometimes released something as kind of a joint effort between himself and Jones. Jones also has someone regularly 'rewrite' his prophecies for him and this is published on his website. Whether this is intended or not, all of these activities 'shield' Jones from the immediate audience and is quite confusing.
Authenticity is critical.
Ownership of the message really resides with Bob, and ethically, it is best for an author or preacher or anyone to have their message authenticly or accurately relayed. Until then, if anyone really wants to know what Bob Jones said, they might have to get taped messages and hear the message for themselves.