I think what makes redbpf stands out is that the other libraries allow you to write the user-space code in Python or Lua etc, but then the kernel code must still be written in C and gets compiled with clang.

In redbpf we let you write the kernel code in Rust as well, and then we have our own LLVM based toolchain to compile that to BPF bytecode.

bpftrace is similar to redbpf in approach, in that it lets you use a DSL instead of C.

Lua is the most common language I had never heard about before dealing with BPF. It gets embedded in a surprising array of technologies.

That's most of what lua's purpose is: to be a reasonably pleasant and featureful language that is dead easy to embed in larger systems that want some kind of scripting or macros.