Viewtop Editor

I was wondering if anyone knew how to gain access to the code of the editor in viewtop so that it could be modified. Likewise with the viewtop itself.
The documentation page states this:
"Its source code is open, so you can enhance it; extend it; learn from it."

Thanks Graham, much appreciated.

This post is for you: http://rebol2.blogspot.it/2012/09/editor-with-undo.html

The post above illustrates the editor script can be directly accessed since it is built in.
Type "help ctx-edit" into the Rebol console.
See www.rebol.net/wiki/Setting_up_in_Linux, the "Modify The In-Built Editor" section.