It's democratisating metatheory! What's not to understand?

I think so. To me it seems like yet another implementation of lambda calculus with a poorly made webpage which does not explain why it is interesting.

This is one of those articles which I hoped would generate an interesting discussion, and hence I upvoted it on that basis.

We ARE on YCombinator here, after all. And there are lambdas there. Good enough?

I upvoted in the hope someone would explain it to me.

Not I, but I upvoted you for telling it how it is.