I've heard many times that copyright of scripts in Hollywood is easily circumvented, as you can't protect a plot, only the specific words.
I came across a good, if somewhat dry, article summarizing the current state of play as regards this: http://www.law360.com/articles/591491/plot-thickens-for-scre...
http://www.tessgerritsen.com/gravity-lawsuit-affects-every-w...