It is actually an addon to Jeditable, an inline (in-place) text editor for jQuery.
The stand-alone, simpler Jeditable jQuery plugin can be downloaded from here.
Basically, whenever the user clicks (double clicks) on a block of text, it will make that text go in edit mode, but instead of a simple input field (textarea), this addon will add a WYSIWYG text editing interface to it.
The WYSIWYG interface is jWYSIWYG, by Juan M. Martinez.
Requirements:
· JavaScript enabled on client side
· jQuery JavaScript Library
· Jeditable