Bookforum has a great in-depth interview with John Barth. A snippet:
BF: Your last novel, Coming Soon!!!, featured a relationship between a professor/ writer approaching retirement and a “novelist aspirant,” as you called him, who challenges his mentor to a collaboration-cum-competition. As a writing instructor for over forty years, with students like Mary Robison and John Casey, did you ever feel threatened by your apprentices’ success?
JB: Oh no, on the contrary. I take avuncular pride in their success. I would always tell them at the end of our time together, after having worked my butt off on their manuscripts and having had them work their butts off on their manuscripts, “Okay, as of today I never want to see another unpublished word from you. But do please send me all of your publications so that I can kvell about them to my colleagues and modestly take partial credit for what you would’ve done anyhow.” No, I have never felt threatened in the least. I’ve had to be careful sometimes that I didn’t accidentally, unintentionally, unconsciously borrow a good metaphor or image or something from one of my students back in the old days, but I don’t think I ever did. At least, I told them, If you ever find anything in my writing that I stole from you, blow the whistle. So far as I know, no whistles have been blown, so I presume that’s never been the case.