The Leo literate text editor is written and Python and appears to be using a syntax highlighting engine compatible with jEdit syntax definitions, which are written as XML. This gives them access to more than a hundred existing mode files.
This means that Factor syntax highlighting managed to sneak into another editor.
The actual implementation doesn't look like jEdit's code at all; I suspect they did a clean-room port because jEdit's Java code is GPL licensed, however I wouldn't mind if they looked at my (rather crappy) code.
A similar highlighter could be implemented in Factor, too. Since jEdit mode files use regexps, Doug Coleman would need to finish his pure Factor regex library first, or a PCRE binding could be developed.