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The new version is more than double the older Mac OSX versions. Does anyone knows why ?

Total Annihilation: Commander Pack 1.3 2.4 GB
Total Annihilation Commander Pack for older Mac OSX versions 1.3 1.1 GB

The windows version is only 1GB, on par with the older Mac OSX versions.
Gcenx83 already answered that in the Changelog topic

7. This is the big one, why in the hell do you have TWO copies of "drive_c" the first one located directly inside the wrapper folder is not needed it should be a alias to the original you doubled the size for the download & install for no reason at all.