
The properties of the Busy Beaver function carry over to any other computational model you could base it on. E.g. the lambda calculus based BBλ[1] shares most of its properties.
> Which immediately reminds me of Chaitin's constant which also tries to encode/talk about the properties of Turing machines,
Chaitin's work on Algorithmic Information Theory (aka Kolmogorov Complexity) was actually focussed on custom Lisp languages of his own design rather than Turing Machines. One could be confused though by some of his articles on LISP program-size complexity like [2] where he calls his LISP interpreter a UTM (Universal Turing Machine).
[2] https://www.jucs.org/jucs_2_5/the_limits_of_mathematics/Chai...
An introductory chapter is available in the "Elements of Information Theory" of Thomas Cover and Joy Thomas.
The field is called "Algorithmic Information Theory" and some of the big names in it are: Ray Solomonoff, Gregory Chaitin, Ming Li, Paul Vitányi, Chris Wallace, David Dowe, Markus Hutter, Jürgen Schmidhuber, Jorma Rissanen, among others. All of these guys are great writers and have breakthrough ideas!
If you are interested in "real world" applications of Kolmogorov complexity, I recommend you to take a look at MDL (Minimum Description Length) and MML (Minimum Message Length).
I hope you will enjoy the references! :)