compiling matplotlib on Snow Leopard / tar error

I tried to follow the instructions given on
and modified the make.osx accordingly to compile matplotlib on OS X 10.6.2 (Snow Leopard).

But after executing
sudo make -f make.osx fetch deps mpl_build mpl_install
I get the following error message:

I had compiled and installed tar from source, so it could be that my tar is missing a binding, but otherwise I could do "tar xfz <file.tar.gz>" on gzip files. zlib and bunzip2 are also installed on my system.

If I do a "cat make.osx | grep tar" to find the possible location of the error in the makefile, I only get:

  rm -rf zlib-${ZLIBVERSION}.tar.gz libpng-${PNGVERSION}.tar.bz2 \
  freetype-${FREETYPEVERSION}.tar.bz2 bdist_mpkg-${BDISTMPKGVERSION}.tar.gz \
  ${PYTHON} -c 'import urllib; urllib.urlretrieve("${ZLIBVERSION}.tar.gz", "zlib-${ZLIBVERSION}.tar.gz")' &&\
  ${PYTHON} -c 'import urllib; urllib.urlretrieve("${PNGVERSION}.tar.bz2", "libpng-${PNGVERSION}.tar.bz2")' &&\
  ${PYTHON} -c 'import urllib; urllib.urlretrieve("${FREETYPEVERSION}.tar.bz2", "freetype-${FREETYPEVERSION}.tar.bz2")'
  tar xvfz zlib-${ZLIBVERSION}.tar.gz &&\
  tar xvfj libpng-${PNGVERSION}.tar.bz2
  tar xvfj freetype-${FREETYPEVERSION}.tar.bz2 &&\

which doesn't give me any hint, since all this formats should be support.

Did anyone encounter this problem?