That's another possibility of course, that you might wish to look into Ender. GTK-HTML doesn't get the same amount of press that KHTML does, but it's written in C and is actually a fairly capable embedded html renderer. It relies upon GTK/GDK which already has a port to Windows, the GNOME help system uses it for rendering afaik so it should be easier to integrate with Wine. Finally it supports editing, which might come in useful in future.
There is actually two different HTML renderers that's used in GNOME gtkhtml and gtkhtml2
GtkHTML was originally a port of a very old version of KHTML to Gtk+. gtkhtml2 was written from scratch.
GtkHTML is used by evolution for both showing html (in html messages) and for editing, in the composer. I think there exist a browser somewhere which use this widget. But as far as i can say i don't think it renders web pages very good.
gtkhtml2 on the other hand is the library used by yelp, the GNOME 2 Help system which support css quite well. But no editing and is more or less unmaintained. At one point in the future it will be abandoned and GNOME will use GtkHTML in the help browser instead.