AFAIK Dillo is GTK-based, at least the UI part, so I don't think so.

	▲	axus 13 hours ago \| parent \| next [-]
		FLTK was a pleasure to use (for uncomplicated software). They also put the latest code on Github: https://github.com/fltk/fltk
	▲	1313ed01 13 hours ago \| parent \| prev [-]
		I just started it up and it turned out to be Dillo 3.0 from 2011. I do not know if it was using FLTK back then, but a quick search says that FLTK has been ported to DOS so that might not be an obstacle for the current developers to keep FreeDOS support if they wanted to.