As per the docs eventstore db should be installed via:
brew cask install eventstore
This is currently returning:
curl: (22) The requested URL returned error: 404
Error: Download failed on Cask ‘eventstore’ with message: Download failed: https://eventstore.org/downloads/macos/EventStore-OSS-MacOS-macOS-v5.0.8.tar.gz
If you visit the above link you can see a 404 too.