There is no law in PA statute that prohibits open carry....that makes it legal by default.
18 cs 6110.1 says anyone over 18 may possess.
Keep in mind that in PA, open carry is not legal in a vehicle.
18 cs 6109
18 Pa.C.S. § 6109: Licenses
(a) Purpose of license.--A license to carry a firearm shall be for the purpose of carrying a firearm concealed on or about one's person or in a vehicle throughout this Commonwealth.