BAT won't work on a Mac. It uses a custom DLL. Mac CIV does not use DLLs. You can install BUG fine. If you want it as a stand alone mod, you have to find where Steam has put the mods that are included with BTS. If you want BUG to load whenever you start up CIV, you want to put it in CustomAssets in your Documents folder. That is where I put mine.
If you haven't already fixed BUG 4.4 to work on your Mac, you have to do a minor edit to make it work. Open the file BugUtil.py in a text editor such as TextWrangler or even TextEdit and
delete line 699. If you don't have a text editor with line numbers, just search for, and delete, the line:
newFunc.__name__ = function.__name__
Then save the file back where it came from.
In case the download that you get does not include manual installation instructions, here they are, modified for Mac OSX. You can't use the installer or exe that come with BUG, they are for Windows.
1. INTRODUCTION
BUG is an unaltered-gameplay mod for Civ4:BTS. This readme covers how to install BUG manually.
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2. INSTALLATION
WARNING: You should never modify or replace the original BTS Assets files.
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AS A MOD
To install BUG as a mod so that you must load it to play, place the folder that contains this README file into your BTS's Mods folder.
~\Program Files\Sid Meier's Civilization 4\Beyond the Sword\Mods
Create the file "BUG Mod" in the Mods folder
Be sure that you do not have a BUG Mod folder inside the BUG Mod folder. It should only be the one level named "BUG Mod".
(This is the disc based location. You will have to find where Steam put the Mods folder and install it there.)
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CUSTOM ASSETS
To install BUG so that it is always active with your games (this will allow you to use it with succession games and games you open from the CivFanatics forum), you must first copy the files and folders from the Assets folder into your CustomAssets folder. Next create a "BUG Mod" folder next to CustomAssets and copy the Info and UserSettings folders into it. Finally, copy the files inside PrivateMaps into BTS's PublicMaps folder.
At each step it is important that you tell it to overwrite files.
\Users\<your user name>\Documents\Civilization IV Beyond the Sword\
CustomAssets <-- folders in Assets go here
BUG Mod <-- create this folder
… Info <-- copy these two folders here
… UserSettings <-- copy these two folders here
PublicMaps <-- copy files from PrivateMaps here
If you want to use BAT or any other mod with a custom DLL on your Mac, you will need to install a virtual Windows machine inside your Mac using a program such as Parallels and purchase the Windows version of CIV to install there. I have done that and it works fine. However, if you want to do this, look in the "CIV - Technical Support" forum for the information about the update that Microsoft did to Windows 7 & 8 in September. CIV disc versions will not work with the update nor with Windows 10 unless you use the work arounds described in the forum. If you use the Steam version, that won't be a problem, since it is the actual disc access that is messed up.
That said, although I have the Windows version of CIV installed via Parallels, I mostly use the Mac version, since I only use a mod with a custom DLL now and then.