No, radiant, quark, and hammer are 'positive' editors. UnrealED and SamEd are hybrid editors, and all proffesional modeling packages are usually used as CSG editors for level building. Jed just happens to be a hybrid editor too, though the mechanism for this - custom 3dos - is a bit clunky because the engine wasn't designed with that style in mind.
Furthermore, it is quite possible to compile JED created maps into quake3 BSPs. But I wasn't even thinking of that. JK isn't the only game that uses that style of sector-and-portal engine. In fact, the Quake engine and all dirivatives, right up to doom3, use a very specialized portal rendering technigue; except they calculate visibility before hand instead of at runtime. CrystalSpace desperatly needs a decent dedicated editor, I'm sure they would adore JED. The JED format could be converted to the descent format too, for use in descent3. A simple compiler could replace the BSP portion of the q3 compiling pipeline, and still utilize the visibility and lighting capabilities of q3map2.
Don't ever assume I don't know what I'm talking about. You will never be correct.