I can't speak to the Ruby details but I used to use the same author's node-packer, which was the same concept for Node.js. It uses libsquash to store the script

I can't speak to the Ruby details but I used to use the same author's node-packer, which was the same concept for Node.js. It uses libsquash to store the script source and replaces the REPL entrypoint to run the embedded source from the internal squashfs. The node.js binaries were about 50 MB which sounds large for hello world but the size would stay practically the same for a full featured application since everything is baked in already. I'd imagine the Ruby version is relatively similar in size but cannot say for sure.