I protest the characterization of Smalltalk as legacy. Seeing Cedar mentioned was very cool - Cedar/Mesa along with Trellis/Owl were environments I was very interested in during my late high school / early college days, though I had no access to either. I do have a lot of Trellis documentation lying around somewhere someone at DEC kindly sent me when I wrote them about it.
I assume you mean this project: https://github.com/rochus-keller/Smalltalk/
It's about a Smalltalk-80 image from 1983.
Trellis/Owl had interesting ideas, though I spent more time with Modula-3.