The module define a permission it doesn't use

You can check this: http://drupal.org/node/206757

I don't think this permission is actually needed. My thinking is that it was included into the module as part of a copy and paste mistake from the tutorial you link to.

The gtranslate_perm() function just details what permissions to create for the module, it doesn't actually do anything with them. I have checked and the permission 'access onthisdate content' isn't being used anywhere within the module so I think it's safe to remove the function entirely. Here is a patch file that will do this:

Index: gtranslate.module
===================================================================
--- gtranslate.module	(revision 107)
+++ gtranslate.module	(working copy)
@@ -13,10 +13,6 @@
     return $output;
 } // function gtranslate_help
 
-function gtranslate_perm() {
-    return array('access onthisdate content');
-} // function gtranslate_perm
-
 function gtranslate_block($op = 'list', $delta = 0) {
     if ($op == 'list') {
         $block[0]['info'] = t('GTranslate');

I am closing this issue, since Drupal 6 isn't supported anymore.