I have chamomile all over my yard and the chickens free range in and around it all the time without any ill effect. I have no idea if they try to eat it or not, I've never seen them munching on it. One caveat though, my chickens free range and have access to a plethora of greens, bugs and whatever else they run across. Chickens in a run with access to only the greens at the fence-line will be more likely to eat those greens, regardless of what they are because they don't have a variety to choose from. For instance, my chickens never eat mint, yet when someone planted it in or around their run the chickens devoured it.
So, proceed with caution. Find out how it might affect them and if possible, provide a variety of greens around the run/coop so they aren't eating just one thing.