This framing is also in the post. From the readme:

> Bonsai itself -- this library -- is actually more generic than the above makes it sound. It allows you to build general-purpose incremental, composable state machines. Bonsai_web builds on top of that core library, specializing it for interactive browser-based UIs, but we also have Bonsai_term for building interactive terminal-based UIs.

The docs are a bit sparing but if you read the source its pretty cool to see how they did this.