AIPS is covered by the Free Software Foundation's General Public License and can be freely redistributed with certain conditions. Read the License (via the previous link) for the details.
Browsers no longer allow ftp access in general. You may access AIPS
ftp site in the old fashioned way by the command
ftp ftp.aoc.nrao.edu
and log in as anonymous with your email as password. Then
cd pub/software/aips
to see all that is available. Much of the documentation material has
now been made directly available to the web at address AIPS/TEXT.
For ftp access, just go to ftp.aoc.nrao.edu
in the /pub/software/aips/ directory and get the README
file.
AIPS is no longer available on tape or CD except by very special arrangement.