I just set up the cache so that you can now run the interpreter for Grace using:
$ nix run github:Gabriella439/grace -- repl
… and if you accept the prompts you'll download and run a cached binary and launch the REPL. Nix makes this pretty slick.
Of course you can do things other than launch the REPL. Just replace repl with --help to see the full set of options.
If you're new to Grace, check out the announcement post:
… or you can also try Grace in your browser: