The Octave distribution includes a 220+ page manual that is also distributed under the terms of the GNU GPL.
The Octave manual is intended to be a complete reference for Octave, but it is not a finished document. If you have problems using it, or find that some topic is not adequately explained, indexed, or cross-referenced, please send a bug report to bug-octave@che.utexas.edu.
Because the Octave manual is written using Texinfo, the complete text of the Octave manual is also available on line using the GNU Info system via the GNU Emacs, info, or xinfo programs, or by using the `help -i' command to start the GNU info browser directly from the Octave prompt.
It is also possible to use WWW browsers such as Mosaic to read the Octave manual (or any other Info file) by using Roar Smith's info2www program to convert GNU Info files to HTML. The source for info2www is available via anonymous ftp from ftp.che.utexas.edu in the directory `/pub/www'.