First, the answer to whether or not an alien would understand the lambda calculus is no different than whether a dog or a dolphin can understand the lambda calc

First, the answer to whether or not an alien would understand the lambda calculus is no different than whether a dog or a dolphin can understand the lambda calculus. It depends on the wiring of their brain. The lambda calculus is recursive; perhaps then self-awareness/self-reference is a prerequisite to understanding. Second, the claim that the lambda calculus was discovered but all programming languages are invented does not take into account LISP, which was both discovered and invented (cf. Paul Graham's "Roots of Lisp" (https://sep.yimg.com/ty/cdn/paulgraham/jmc.ps?t=1564708198& https://sep.yimg.com/ty/cdn/paulgraham/jmc.ps?t=1564708198&).