Mention Gruber's regexp in the LICENSE.

LICENSE

@@ -34,5 +34,8 @@ audio/beep.wav from http://freesound.org/people/pierrecartoons1979/sounds/90112/
 Font Awesome by Dave Gandy (http://fontawesome.io)
   license: http://fontawesome.io/license/
 
+URL-matching regular expression by John Gruber (http://df4.us/fv9)
+  "Consider it public domain."
+
 seaweedchan/4chan-x (https://github.com/seaweedchan/4chan-x)
   license: https://github.com/seaweedchan/4chan-x/blob/master/LICENSE

src/Linkification/Linkify.coffee

@@ -3,7 +3,7 @@ Linkify =
     return if g.VIEW is 'catalog' or !Conf['Linkify']
 
     # gruber revised + magnet support
-    # http://rodneyrehm.de/t/url-regex.html
+    # http://df4.us/fv9
     @catchAll = /\b([a-z][\w-]+:(\/{1,3}|[a-z0-9%]|\?(dn|x[lts]|as|kt|mt|tr)=)|www\d{0,3}\.|[a-z0-9.\-]+\.[a-z]{2,4}\/)([^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’])/g
 
     Post::callbacks.push