Fluxus has been unmaintained for a very long time. The last time I worked on it (years ago), I remember it compiled only with a really old version of Racket (I think Racket v4).

Here's an old video of what Fluxus looks like https://www.youtube.com/watch?v=2O5DJTOy6EA. The video quality is bad. But the 3D stuff is clearly visible. The user in the video is typing into Fluxus from the beginning of the video. The documentation for Fluxus as I remember was some large PDF file.

Anyone else know of similar live-coding environments for 3D?

P.S: I do love using Three.js.