This one: " The license granted hereunder will terminate, automatically and without notice, ..... (b) that any right in any patent claim of Facebook is invalid

This one: " The license granted hereunder will terminate, automatically and without notice, ..... (b) that any right in any patent claim of Facebook is invalid" Basically if you accept Facebook's license, your right to use Facebook-patented software will terminate, in case you express your view that some other (any) Facebook patent is not valid (say due to prior art).