Nice writeup, short so is more approachable than John Koza’s classic book on GP. That said, if GP looks useful to you, eventually read Koza’s book, or at least experiment with his Common Lisp code.
Also don’t confuse Genetic Algorithms (GA) with GP.
There's some minor issues with the blog post though that don't make it entirely correct Genetic Programming as written by Koza's. I'd have to dive into it again but I think it was either with the way mutations are done or how fitness is evaluated.
Also don’t confuse Genetic Algorithms (GA) with GP.