gwrkvm5.2.1ce.tar.gz does not properly extract. In windows, powerarchiver simply reports an error extracting the archive. In linux, it reports:
paragon ~ # tar xzf gwrkvm5.2.1ce.tar.gz


gzip: stdin: unexpected end of file
tar: Unexpected EOF in archive
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now

I am not the only one having the problem. See http://www.groundworkopensource.com/community/forums/viewtopic.php?f=21&t=1755&sid=7945ebf9c1f184a85dfb588c72e72e51