I used to play them (PSAs) when I worked in programming at a small TV station. Lots of groups send in :30s and :60s and the station is required by the FCC to devote some small percentage of their air time (like 2-3% I recall) to these.
I would get lots from the LDS aka Mormon Church, ones on recycling, etc. I have seen the WT Society 30 second TV ads, they actually have done a few of them they are similar to the Mormon ones.
And yes any non-profit (or non-prophet lol) group can send them in and they might get played for free. I generally tossed all the lot except for the environmental and recycling ones.