While this does basicly nothing that different (except add a lot of additional files + waste to your vbulletin directory) , why are you replacing the default class_bbcode.php and class_bbcode_alt.php files ? That's just a bad idea to begin with.
Besides after looking through the code, your vbulletin_config.php file adds a define for the path to the itemstats folder (which should be in the init_start hook), and your other include , the vbulletin_itemstats.php file is completly empty (0-byte file).
Anyways, for the question above as to what the difference between gItemStats and my product?
Using
wowheads powered by javascript does not add additional code to your site. the ItemStats mod adds a table to each for each item link that is created embeded into the item's A HREF tag. If you have a rather large item list (such as say your guild bank listing or even your own characters listing), you could increase the size of your page download by quite a bit.
Also, editing a post with an item in it using the WYSIWYG editor clobbers the item link.