It's equivalent to binary machine code for a procesor with 5 opcodes.

Why would it be readable?

No kidding.. I didn't think parenthesis hell could get worse than Lisp

Well really this language just takes the next logical step by removing all but a single symbol.

The next one would be () = t, to finally get a language consisting solely of parentheses.

Any source code in any programming language can in theory be encoded in unary, requiring only a single symbol (and without any need for extra grouping or whitespace). It's not gonna be efficient, though.

Yeah, I think I'm going to take the author's advice and use Tree Calculus to generate JSON config files. That way I won't need to use a bloated tool with a JSON parser just to output configuration.