And no, you do not need to install Ruby - it's already installed, and you may not need to install boost as I believe gtk needs it - but it never hurts to run that line. Just ideally do NOT install the ports version of Ruby, use the Apple-provided version or use rvm!
If you're that gunshy, you can try this:
https://drive.google.com/file/d/0B0G...ew?usp=sharing