Change tar to GNU

  Hi,

  I have backup script build with tar and -newer options.
on FreeBSD 4.x it worked and i see:
$tar --version
tar (GNU tar) 1.13.25

on FreeBSD 5.3 not working and I found:
$tar --version
bsdtar 1.01.011, libarchive 1.01.013
Copyright (C) 2003-2004 Tim Kientzle

So I understand that you change own tar to make different licence.

I just thinking what is proper way to update tar to GNU tar to make 
working again my script?

thanks,

Casper