It is commercial and does offer a trial to try it first
also.
I found Amanda rather complex for what we
wanted to do (simple backup of a single server to a single tape
drive).
We eventually decided on BRU (www.tolisgroup.com). It's not free, but the
simple 'workstation' version isn't very expensive.
Their support staff are
really helpful as well. Free download for trial if you
wish.