Where can you get GMO free feed? Countryside Organics here in Waynesboro, VA sells what you need and will ship their feed. I wouldn't feed my chickens GMO feed, but that's up to you for your chickens.
There is no "proof" that GMOs are harming human health because the biotech companies won't let the research be done. You don't hear about GMOs in mainstream media because the biotech companies have threatened the news organizations who have tried to do stories on the effects of GMOs. The few studies that have been done with rats have pretty significant results.
If you don't want GMOs in your diet, don't eat them. If enough of us avoid them, the biotech companies will change their tune. That's what happened in Britain. How do you avoid GMOs? Don't eat soy, corn, canola, sugar (unless it is specified as cane sugar), aspartame, and papaya, or any of their derivatives, unless they are organic or Non-GMO Project verified (or both). That means reading labels and eating very little processed foods, but your health will be better, both because you won't be eating GMOs and you'll be eating fewer processed foods. Also, some summer squash/zucchini has been genetically modified, so its best to get that organic or grow your own from seed that's organic or labeled non-GMO. Soon farmed salmon will be GMO and you'll need to avoid it.
GMO crops have been modified so that they are resistant to herbicides, such as round-up, or so that they produce their own toxin to kill insects. The ones that are resistant to herbicides are heavily sprayed with these. The ones that produce their own pesticides kill many beneficial insects in addition to the pest insects. Bees who collect the pollen from corn, for example, have suffered from the results of the toxins in the pollen.
If you want to know more about GMOs check out the Institute for Responsible Technology,
www.responsibletechnology.org