http://members.aol.com/ukandrewc/rtftext/features.htm

"Need to edit RTF in your application? The control is based on the popular richedit class. It adds all the essential functionality to create a complete embedded RTF word processor. "

I suspect that gnucleus is using a class for rich edit (not this particular one) to display some text or help text and that may be in a dll on most systems.

Try installing ms word and adobe pdf reader again