Dixie Chicks' Natalie Maine also on hand to see three men plead guilty and walk free.
Artists who believe trio were wrongly convicted of murder team up for compilation album.
Guitarist/bandleader says he is 'healthier than ever and beating' the disease.
Much of what made the concert tick took place offstage.
Line-ups for shows on four continents were announced Friday.
Meanwhile, Rage Against the Machine offered the most explicit politics while Garbage and Blur got Dutch fans onto their feet.