The parking area, all areas within a 1/4 of a flowing stream and most of the mountain, outside the several cabins is in a forest protection area. Camping at the TH could result in a fine and they are patrolled. Check with the Saco ranger district
Didn't see signs specifically saying no overnight that I can recall. It's more of a remote trial head, but wouldn't be surprised if it's technically not allowed. Ymmv.
Thanks! Your answer is awaiting moderation.