These lisp files should work under recent versions (19 onwards) of both Emacs and XEmacs. See the Octave documentation (info node `Emacs') on how to install and use these packages.
These files use the custom package so that user variables can be changed easily. The custom package has been included in Emacs since around version 19.34. If you have an old version of Emacs without the custom package, you should get the following error when trying to load the octave files:
Cannot open load file: custom
In this case, you should use the simple replacement custom library here, renaming it to custom.el so that Emacs can find it:
% mv custom-old.el custom.el
But remember when you upgrade Emacs to version 20 and beyond, you should delete this primitive custom file and use the built-in version instead.