TAB / Garnier Limb installation - Nelson Treehouse says to coat with WD-40 prior to screwing it in (5:34 of this video) - will that not cause harm to the tree?
How to Install a Treehouse Attachment Bolt (TAB) - Installation Video
Tree Houses – Cool Tools
Garnier Limb History - Out N About Treesort
How do you build stuff in trees? Part 1. - by Jeff Waldman