An updated homebrew-iojs formula is maintained by @aredridel and is available with just one command.
brew install aredridel/iojs/iojs
Default formula
As of iojs 2.0.2, Homebrew ships with its own formula for iojs. This isn’t preferrable, in my opinion, since global npm packages aren’t being ran properly.
If you’d like to use this anyway, simply doing brew install iojs is not enough. To get iojs working on Homebrew You will need to unlink node first then use link --force to install iojs.
brew install iojs
brew unlink node
brew link iojs --force