It is not very clever - I know, because I wrote it.
All it tries to do is to put files where they want to be. It was originally developed for installing vanilla Civ3 mods. These required you to put pieces of the mod into two or three different subfolders without deleting any existing folders, which was a very error-prone process if done by hand. So the ModInstaller was pretty neat in the day. With more recent versions of Civ3 and Civ4 this is largely a thing of the past.
For Civ4, if you can get the files extracted into a single mod folder then all you have to do is drop that lot into ~/Civilization IV/Mods/, or maybe ~/Civilization IV/CustomAssets/.
The only possible excuse for wanting something like ModInstaller now is where you have a patch for an installed mod. Then the patch files and folders may need to be distributed around the existing folder structure.
I haven't done any serious work to get ModInstaller to do this well for Civ4. In the early days, people seemed to want an easy way to get BlueMarble into the right place, so I adapted it to put CustomAssets mods in the right place, but I doubt if it's much use for anything else.
The other disincentive to doing anything about adapting ModInstaller for Civ4 is that getting the files in the right place is usually the least of your worries when installing a mod, and FfH is no exception. Most mods use a custom CvGameCoreDLL.dll file these days, and the Mac version of Civ4 simply CANNOT deal with those, so you are dead in the water if your target mod contains a file of that name. FfH does, I believe. Even if your mod doesn't have the dreaded DLL, chances are that it will not load properly because of problems with the XML or Python code. These are usually fixable, but if you have the expertise to do that, then putting the files in the right place is child's play.
