http://ratfactor.com/forth/the_programming_language_that_writes_itself.html
An exploration of the evolution and meaning of the Forth programming language and its context in history.
Forth, its history and the computer science ideas which form its foundations explained in a light and humorous style sprinkled with links to interesting resources on the web.
Forth is a neat little language. Writing a compiler for it is very easy, and yet it isn't too terrible to write as a user. That is a tough balance to strike.
Emphasis on the "little". You can get a working Forth environment into <5K. That's why they used to use it to write BIOSen. I'm surprised you don't hear more about it in embedded spaces today—seems like it would be ideal for that use case.
Do I need to understand lambda calculus to get the most out of this article? I made it to combinators and I’m a bit lost. Should I just read the mentioned “to mock a mockingbird”?
lambda calculus
I wouldn't say so. I'd say you can try quickly skimming through the theoretical explanation and instead reading the code snippets provided. I've got a feeling that you're already familiar with the concept and can figure out the code - it's just the math behind it which can read too intense.
I don't understand λ calculus, but I was able to make it through the article. It gets less theoretical and more about how Forth works, why it was designed the way it is, and so on. It was a great read!