So happy to have stumbled upon this, this is truly awesome, a recounting of Lucid's creation and various details by one of its creators. Probably best to start at the beginning:

https://billwadge.wordpress.com/2011/03/23/lucid-the-origins...

And then work your way forward. The book is also great: http://www.cse.unsw.edu.au/~plaice/archive/WWW/1985/B-AP85-L...

This stuff has a very direct line to the modern "FRP" ideas (with the exception of the actual FRP by Conal Eliot, which is actually quite different from what most of us call FRP, oh details...). And it's so much more cogent.

Also check out the Wikipedia page: https://en.wikipedia.org/wiki/Lucid_(programming_language)

When I looked at it a while ago, I couldn't find a working implementation, so I banged on it until I got something that at least appeared to work (on OS X): https://github.com/mpw/pLucid-osx