If you have never run Mathematica, run the following bash commands in your terminal:
echo "!license.engr.ucsb.edu" > ~/.Mathematica/Licensing/mathpass
/ece/Mathematica/9.01/Executables/mathematica --pwfile ~/.Mathematica/Licensing/mathpass
Note: Software downloads available ONLY from UCSB campus networks. If you are trying to download while connected to the campus wireless, you must use the campus vpn service (http://www.oit.ucsb.edu/network_services/VPN_service/).