The Appalachian Trail does have some places along the trailer where you can camp for free without permits or fees.
And there's no fees or permits to be able to walk or hike the Appalachian Trail.
However the Appalachian Trail does pass throughout numerous state and national parks, forests and public lands.
Some of those camping places do require permits or fees to camp at however there are some other places that do not require any permits or fees to camp.
Still it's a good idea to have some money on you in the event you do hike and plan to camp somewhere along the Appalachian Trail where permits or fees are required.
I've never hiked the entire Appalachian Trail so whenever I was hiking it I found a few places for free to camp.
But if I were to go any further then I would probably reach a place on the Appalachian Trail where I was required to have a permit or pay a fee to camp.