Not the author, but you can hack on it - you just have to install Rust!

Another editor worth mentioning here is Micro (https://micro-editor.github.io/), written in Go, which is also a TUI editor, is hackable not only because open source but also in the sense you mentioned (with plugins written in Lua), and (exceptionally for a TUI editor) it has the "usual" default keybindings that all of us non-Vim and non-Emacs diehards are accustomed to (Ctrl+S for save, Ctrl+F for find etc. etc.).