Meh. Github was shows a 404 if the user isn't signed in.

docs/index.html

@@ -128,9 +128,9 @@
 
 			button.addEventListener( 'click', function ( event ) {
 
-				window.open( 'https://github.com/mrdoob/three.js/edit/dev/docs/api/' + path + '.html' );
+				window.open( 'https://github.com/mrdoob/three.js/blob/dev/docs/api/' + path + '.html' );
 
-			} );
+			}, false );
 
 			var pages = {
 				"Integer": "Integer",