It may have changed, but I believe the plan is to bundle the headless agent with CallManager 3.3(3). Being a headless agent, it will provide all the security benefits of a fully managed solution. The difference is that the headless agent doesn't have any reporting capabilities. The option to upgrade to a fully managed agent will be available.
Your account team will likely have the details for you.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.