Yes Ziploc freezer bags are BPA free.
All Ziploc bags including Ziploc Freezer Bags are BPA free and contain nothing toxic in them that could harm your health when the food comes into contact with the bag.
Not only are Ziploc bags BPA free but also the Ziploc containers are also BPA Free as well as many other food bags and food containers contain no BPA.
The Ziploc bag brand company products are extensively evaluated for toxicity and safety and comply with applicable quality and safety regulation.
So that makes the Ziploc bags safe for food to be stored in otherwise they would likely not be able to sell those bags today.