With regard to the UG I assume its something I've not read.
The UG comes from the name of the mod and means Unaltered Gameplay. The number one tenet of the BUG mod is that it a) doesn't alter any game rules or mechanics and b) doesn't provide information not already available in the normal game. What BUG
does do is present the same information in a more easily-understood manner and provide alerts for when certain things have or are about to change.
The bug I mentioned 2 posts above occurs in our Military Advisor's new Sit-Rep page. This page gives you a quick overview of each of your rivals with regards to their military situation (Situation Report). Specifically, it has two "Strategic Advantages" columns that display which units you can build that they cannot and vice versa.
For example, say you have Iron Working and access to Iron, but your rival does not. On the other hand, your rival has Construction and access to Ivory. You are connected to their trade network and thus can see which resources they have available. Your SA column will show a Swordsman icon, and your rival's SA column with show a Catapult and War Elephant.
The issue I found is that in a certain case -- you don't know of any coastal AI cities, but they do have at least one and can build boats -- their SA column will show the boats they can build that you cannot. This tells you that they have a coastal city that you do not know about. This is what we call "leaking information" because it gives the player information that they don't normally get.
This doesn't apply to land or air units because you can build those in any city, and any civ that is still alive must have at least one city. Therefore, it's not giving you any information you don't already know.