Hacker News Reader

It's a lisp dialect form the MIT called scheme. You can find more information here: https://www.gnu.org/software/mit-scheme/

I guess racket is where the development continues for the scheme language.

There are a few: Gambit, Chicken-Scheme, Chez-Scheme, and Racket. Racket is starting to purposely diverge though like Pharo is to Smalltalk.

Racket has official support for R5RS and R6RS, and unofficial support for R7RS-S. So you can program in scheme in with the Racket environment too.

You also have GNU Guile, if you for whatever reason prefer the GNU stack.