Anything tied around the trunk or branches will damage a large area of bark as the tree moves, and if tied around the whole branch will gradually strangle the branch. You may have seen fence wire that was wrapped around the tree many years ago and has since been grown over completely. Trees can sometimes grow over obstacles, but it is much better to completely avoid the risk of killing them.
A lot of people use ropes to fix treehouses so that they "don't hurt the tree", but the damage the ropes actually do is much greater in the long run. Ropes should only ever be considered for very lightweight treehouses that will be taken down each year to relieve the pressure on the bark. Using wide webbing straps or slings will help to spread the load over a greater area.