See nathan-v/aws_okta_keyman for more information.
Formula installs AWS Okta Keyman v0.8.4
brew tap nathan-v/aws-okta-keyman and then brew install aws_okta_keyman.
Or install via URL (which will not receive updates):
brew install https://raw.githubusercontent.com/nathan-v/homebrew-aws-okta-keyman/master/Formula/aws_okta_keyman.rb
brew help, man brew or check Homebrew's documentation.