There's still a sign for Collaberative in The Path of Heroes, even though it's no longer in FFA. I didn't try to join it and find out what would happen for fear of losing my progress.
Server IP: zero.minr.org
Who are we?
We are minecraft's 3rd oldest server and the oldest dedicated challenge and parkour server in the world. Our map dates over 10 years and our server has had an uptime of 99%. We have over 400 challenges which will keep you occupied for months. All of our challenges have been created by our member base who have completed our Hardcore maps. You yourself could one day be creating a challenge for our server, if you ever achieve the green membership rank.