I originally bought sisal twine and then heard that some people had trouble with the jute and sisal twine not lasting the entire season and breaking.It'll work fine. I'm going to go with the jute or sisal rope at the local home improvement store only because I dont' have a free source like you do. They'll climb anything just make sure it won't break.
yes, i guess we would call that more of a rope than a twine.... still not the sort of rope we had to climb (or failed to climb in my case) in gym class...It sounds like you were using sisal rope then? The rope is strands of twine twisted together...or that's the way I understand it. I had bought sisal twine that was about 1/16th of an inch! That's why I upgraded because after I strung it up it didnt seem like much. I think if you're using sisal rope you'll be fine but have to replace it every couple seasons or so.
Not sure, I'm just going by what I've read.