This has been about 6 years ago now, but at the time there was a BBQ rub store in the Burlington (ia) mall. One time the owner provided me all the meat and a boat load of rubs to cook, and then distribute. I also did a cooking demonstation about ribs. I contacted the Des Moines County HD, and because the food was being given away and no $$$'s were being charged, I didn't even need to have a temporary permit.
Again this was years ago, and since then I have a mobile food kitchen that is fully licensed and compliant so I haven't really followed the law since then.
I will say that HD codes in Iowa are tightening.