I camp there all the time, but not for free. Both the
commercial and White Mountain National Forest campgrounds
charge. In fact, even parking isn't free - the sticker
costs $20/year. On the other hand, unlike the Gunks, the
climbing is free. Also, theft is not uncommon.
It is legal to camp in the national forest a quarter
mile from roads and trails, but I can't imagine doing that
for a whole summer. What would you do for water, etc ?
At the far end of the Kancamagus Highway near the Rocky
Gorge, there are some cliffs high over the river and two
WMNF campgrounds, one is covered bridge. Ed Webster's
climbing guidebook details the climbs here. I think you
might be able to hike way back in there and live in total
squalor for a while, and hawl your water from the river.
Whitehorse, Cathedral, etc are only a short drive from
there on the westside road.