Automatic installation of the ARC library

As a utility to help deployment (there are already a lot of different dependencies) I've added a small button that will remotely install the ARC2 library.
I FULLY understand if there are philosophical reasons why someone may not like this function, but my use-case is to do a lot of deployment testing, including tear-down and migration of sites, while still trying to keep up with the DEV versions via CVS. Copying third-party libraries around is a PITA.

Anyway:

Code looks like:

/**
 * Attempt to install and unzip the required library from remote source.
 * This may have security implications - it won't work if you have correctly
 * locked-down file permissions. It could if you are on a looser dev box.
 * 
 * There may be various problems on different machines, but this may work.
 */
function rdf_admin_install_arc() {
  $arc_library_package_url = 'http://arc.semsol.org/download/2009/03/05/arc.zip';
  $destination_filepath = dirname(RDF_ARC2_PATH) .'/'. basename($arc_library_package_url);
  drupal_set_message(t('Requesting ARC2 package from !arc_package', array('!arc_package' => l($arc_library_package_url, $arc_library_package_url))));
  if ($package_data = file_get_contents($arc_library_package_url)) {
    file_put_contents($destination_filepath, $package_data);
    drupal_set_message(t('Fetched library to %destination_filepath', array('%destination_filepath' => $destination_filepath)));
    // unpack it 
    // try system-level unzip (did not try eith ZipArchive)
    drupal_set_message(t('Unpacking using commandline'));
    exec("cd ". dirname($destination_filepath) .";unzip '". basename($destination_filepath) ."'");
    if (file_exists(RDF_ARC2_PATH. '/ARC2.php')) {
      exec("chmod -R g+w ". RDF_ARC2_PATH );
      drupal_set_message(t('Success!'));
    } 
    else {
      drupal_set_message(t('Failed to unzip. You\'ll have to do it yourself.'));
    }
  }
  else {
    drupal_set_message(t('Failed to retrieve package from @arc_package',  array('@arc_package' => l($arc_library_package_url, $arc_library_package_url))), 'error');
  }
}

The ARC library is fully GPL, so COULD be distributed. But this method still skirts the distribution issue by not includingit, just providing a tool that does the including for you.
Of course, there are security issues too.
I want this RDF initiative to gain momentum, but that won't happen while the dependencies are such a hassle.

An alternative, using form_alter, is in my sandbox.
If this looks like a bad idea, I'll just leave the code here as an FYI for reference.