As a patch you can use the following script:
#!/bin/sh
#me he ayudado de http://tex.stackexchange.com/questions/30307/how-to-install-latex-zip-package-from-ctan-using-texhash-on-a-nix-system
#listado de archivos tds disponibles: http://www.ctan.org/tex-archive/install/macros/latex/contrib
DIR_TEX=$(kpsewhich --expand-var '$TEXMFMAIN') #Devuelve el directorio donde TeX está instalado, en mi caso /usr/share/texmf
PAQUETE="memoir"
if [ $PAQUETE = "oberdiek" -o $PAQUETE = "environ" -o $PAQUETE = "footmisc" -o $PAQUETE = "hyperref" -o $PAQUETE = "titlesec" -o $PAQUETE = "tocloft" -o $PAQUETE = "enumitem" -o $PAQUETE = "fmtcount" -o $PAQUETE = "glossaries" -o $PAQUETE = "datatool" -o $PAQUETE = "caption" -o $PAQUETE = "babel" -o "memoir" ] ; then #algunos paquetes están en /usr/share/texmf-texlive
DIR_TEX=$(kpsewhich --expand-var '$TEXMFDIST')
#DIR_TEX="$DIR_TEX-texlive"
fi
if [ ! -f "$PAQUETE.tds.zip" ] ; then
if [ $PAQUETE = "babel" ] ; then
wget http://www.ctan.org/tex-archive/macros/latex/contrib/latex-tds/$PAQUETE.tds.zip
else
wget http://mirrors.ctan.org/install/macros/latex/contrib/$PAQUETE.tds.zip
fi
fi
unzip -o $PAQUETE.tds.zip -d $DIR_TEX
test -e $DIR_TEX/ls-R && texhash $DIR_TEX
#echo $DIR_TEX
This was done to be used with GNU/Linux, but probably with some minor fixes (like getting wget) will work in Mac.
It can be used to update and install other packages as well.
Unfortunately whether to install in TEXMFMAIN or TEXMFDIST is not automatical, although most of them, like the one you want, goes in TEXMFDIST.
That's why I would recommend you to find a proper updater with your distribution that does things automatically.
LaTeX
packages are intricately related- it is often not as simple as downloading one file, as there are dependencies. In most cases, the package manager will account for these :)