I don't think you need to modify the signature code to work with vbulletin. All it should do is create a linkable image. For the record, that guild and character listing will work with vbadvanced. I got it working for my guild's vbadvanced web site.
For just a signature, there's a php file
here that you can modify. I did not write this, but bookmarked it from the soe eq2 forums. Can't find the original link to the post.