I don't think they're talking about a released build, but rather building it yourself from source (http://madcoderspeak.blogspot.com/2009/06/how-to-compile-rub...) which is what all mac and linux users do. Even the ruby package managers we use (i.e. ruby-install, rvm, etc.) don't have pre-built binaries, they download tagged source files with checksums and run build commands.