The new defaults for wowza Streaming Engine is for it to start automatically as a service after the installer runs.
It's most likely that is what has happened and then you are getting a port conflict when you try to start it through the terminal.
Run the following commands to shut down the service on the mac.
sudo launchctl unload -w /Library/LaunchDaemons/com.wowza.WowzaStreamingEngine.plist
If you don't want it to start automatically then you will also have to edit the plist files and set each to disabled and not start on boot.
sudo launchctl unload -w /Library/LaunchDaemons/com.wowza.WowzaStreamingEngineManager.plist