Octave for other Unix systems
For other Unix systems you may have to build Octave from source.
FreeBSD
The easiest way to obtain GNU Octave is to install the precompiled package as root user:
pkg_add -r octave
Another possibility is to build Octave from source via Ports[1]. Make sure you have your Port tree updated. Check FreeBSD documentation about how to do that. Then, as root, type:
cd /usr/ports/math/octave make install clean
Some Octave Forge packages can be installed in the same way:
pkg_add -r octave-forge
or via Ports[2].
OpenBSD
Octave can be installed on OpenBSD by installing the precompiled package or by building from source.
The Octave package for OpenBSD is currently at version 3.0.5. Install it as root:
pkg_add octave
Building from source on OpenBSD takes a bit of work at the moment, see Compiling on OpenBSD for more details.