Really interesting! Much of the active "prior art" in data flow languages is in audio and music, where systems like Max/MSP [1] and Pure Data [2] have made several generations of musicians into programmers without even telling them they were programming!

My long-running personal project MFP [3] looks at basically the same problem as FMJ -- visually representing data flow programs with a "real" language under the hood -- but using Python as the underlying language runtime and adopting the graphical conventions of Pure Data.

Great to see interest in dataflow programming. It really is a good way to turn your programming mind inside out.

[1] https://en.wikipedia.org/Max_(software)

[2] http://puredata.info/

[3] https://github.com/bgribble/MFP