I studied at PUC-Rio and I met Roberto Ierusalimschy (the main author of Lua) when he was teaching a course on semantics. I once asked him if I could send a PR about a feature I wanted in the language and he said something that I never forgot: "Yes, but I won't use your code. I love that people send me ideas, but I actually enjoy coding... so I will gladly take your suggestions, though I will write it myself."

He then explained this "dictatorial" behavior is what allowed him to keep the implementation simple and concise over the years. At the time he boasted about the source code being less than 8K LOC, though it has likely increased in recent versions. (I think it was around version 3.) I'd recommend taking a look at the source code, it's truly a C masterpiece.