--- OutputPage.php	2011-11-30 19:44:14.847173341 +0100
+++ OutputPageGut.php	2011-11-30 19:43:43.000000000 +0100
@@ -2062,7 +2062,7 @@
 		}
 
 		// Show source, if supplied
-		if( is_string( $source )) {
+		if( is_string( $source ) && $wgUser->isAllowed('edit')) {
 			$this->addWikiMsg( 'viewsourcetext' );
 
 			$params = array(