Well, I can unequivocally say that the interest I had in Ciao as of a few days ago has utterly vanished as a result of hearing that Emacs is, for all practical purposes, required.
Just to clarify things: Ciao does not require emacs in any way! The top level, the debugger, the standalone compiler, the documenter, the preprocessor, etc. are all command line tools and can all be used from a terminal, from a Makefile, or from a script for that matter.
The reason why line editing and command history are not provided directly by the Ciao top level is because we have always believed that this is an orthogonal functionality that people like to get in their different, favourite ways (rlwrap, emacs, vim, eclipse, etc.). E.g., if you would like to have command line editing in a terminal, a simple way is to use rlwrap around the top level:
rlwarp ciao
And you can always just use emacs as a glorified terminal with:
emacs -f ciao
(this should just start a window with the top level).
Regarding help, the Ciao manuals are in pdf and html and are very well indexed so it is straightforward to find help on anything, be it through the indexes or using search --no need for emacs! There are simple man pages for the command line tools, although admittedly they mostly point to the 'real' manuals available in pdf or html (or inf).
Having said all that, we also provide a very nice graphical environment, based on emacs, which gives you many other things. People have also developed a Ciao environment for Eclipse with syntax coloring, source debugging, etc., and which is also used for other systems supporting Prolog, and there is Prolog support in vim, etc.
Hope this helps people out there -- we will be glad to provide more help on how to use Ciao from the command line if needed. Also, as Jose pointed out, if there is user demand for including editing and manual access directly in the top level, it is straightforward to do, so please let us know!
Manuel Hermenegildo