The Turbo memoization framework sounds interesting, but I don't see any code samples for what it looks like for Rust users, or how it compares to other Rust memoization/caching libraries…

In several places it is mentioned as a Rust library, but I don't see any links to it. Using google search I'm not finding a Rust library named "Turbo". Is the library open source, or available on crates.io / in a public repo somewhere?

Right, they link to this docs page when referring to the memoization library: https://turbo.build/pack/docs/core-concepts

And the github link at the top of the page links here: https://github.com/vercel/turbo but, despite being called "turbo", that seems to actually be the repo for Turbopack (the webpack alternative) not "Turbo" the library.

Even digging a bit into the crates, I'm not sure where this supposed library lives: https://github.com/vercel/turbo/tree/main/crates