These formulae duplicate software provided by OS X, though may provide more recent or bugfix versions.
brew install homebrew/dupes/<formula>
Or brew tap homebrew/dupes and then brew install <formula>.
Or install via URL (which will not receive updates):
brew install https://raw.githubusercontent.com/Homebrew/homebrew-dupes/master/<formula>.rb
brew help, man brew or check Homebrew's documentation.