One of the cool things about CMUCL is how its code is almost entirely in the public domain, and the parts that aren't tend to be a simple 2-clause BSD license. That's how you know the contributors do it out of love for the language and implementation :)
The implementation was originally a university project (financially supported by DARPA) with a team funded to work on that implementation. Scott Fahlman was the lead and it was important for him that the implementation, its documents and its IDE was publicly available.
FYI, if you're just looking for a Common Lisp implementation for Apple Silicon, there is SBCL (which is a fork of CMU Common Lisp): https://www.sbcl.org/
highly unlikely, at this point cmucl support is a one man project by Raymond Toy. in order for the apple silicon to be supported two things need to happen, cmucl needs to be extended to support 64-bit and it needs to be ported to arm, both are major undertakings
well, it's funny because cmucl is a very sophisticated compiler. even a decade ago, back when things like Haskell or ocaml were considered to be "fringe" languages, beating cmucl was an achievement. with type annotations and knowing what you're doing, you can make it perform in the ballpark of C
The same applies to SBCL (a fork of CMUCL) which has more active development now. The funny thing is that the name of the compiler is Python. But this Python actually produces fast programs :) .
