I don't know about other parts of the country, but here, there are certain land-uses that are allowed within each zone that you don't need to get a permit for. On the other hand, our zoning codes are written such that anything not explicitly listed in the zoning code is actually prohibited. As a zoning administrator, I would say that a lot of the armchair lawyering in this thread has some merit. If I were the owner of the business or the OP, I would argue that homebrewing does not create more impact than having an employee kitchen/lunchroom in the warehouse.