I have the full R2 system (inc the editor source code) that was put in the code archives ages ago, so I assume it's public domain and thus free for anyone to use / modify and I can repost it all?
I could be speaking outta my butt since I haven't checked this, but from memory it required F-UI and wouldn't compile without it.
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Okay, so I took the time to check. You can get some more details (including Noel telling everyone how not-particularly-complete the editor is, even when compiled) and a couple of working compiled links here.