Earlier quoted context omitted.
While true in general, public radio has quite a quantity of paid-third-party-ads these days. And they don't just say "supported by [corporation, tag line]", they are full ads, just read by the public radio hosts. There's one radio station group that has consistently been fully public interest with neither ads nor corporate nor government conflicts-of-interest: the Pacifica network which has affiliates around the coun…
Thanks for the link. WFMU also runs no ads and has no corporate sponsors. "WFMU’s primary source of support comes from listener contributions made during our annual on-air fundraising marathonand revenue generated from our annual Record Fair. WFMU does not accept underwriting or corporate sponsorships. We receive some support from foundations and government grants, as long as they do not contain conditions that deter…
It seems that ads were also a motivation for the long-running show JM in the AM to leave the station.
> WFMU, licensed as a non-profit radio station, adheres to the guidelines of charitable and non-commercial radio. With the move of ‘JM in the AM’ exclusively to NSN, the program, its host, its content and its reach will be allowed greater creative flexibility and sponsorship opportunities. [1]
[1] http://www.nachumsegal.com/historic-jm-announcement-made-mor...