This might be an over-simplification but Prison Radio appears to be short (2-3 minutes) recordings made by prison inmates. I’m assuming these are made from phone calls the prisoners are allowed to make. That’s make take on the what, your guess is as good as mine on the ‘why’ but I’m assuming the idea is to give a voice to the incarcerated.
One of the prisoners recording these commentaries is James Keown. Mr. Keown is from Jefferson City, MO, the town where I live. In 2008 he was convicted of murder for poisoning his wife with Gatorade spiked with antifreeze. He’s serving a life prison sentence in Massachusetts.
In one of his three commentaries (Who Are You?) he describes being on the air at one of our local radio stations when, during a commercial break, he was arrested. I briefly met Keown a couple of times but didn’t know him.
I find these commentaries bizarre in a way I can’t quite put into words. Perhaps it’s the distinctive “announcer voice” Keown uses when making the recordings.
UPDATE (1/9/18): Keown has stopped updating his Prison Radio page. Just those three posts back in 2016. His appeal to the Massachusetts Supreme Judicial Court was rejected on October 23, 2017.