What you are installing
BlueBubbles is an open-source project for using iMessage on Windows, Linux and Android. Its setup includes a macOS server, permissions, network configuration and notification setup. The absence of a software subscription does not eliminate the cost of the Mac or the time needed to maintain it.
An agent adds responsibilities
An assistant connected to a personal messaging environment needs careful scoping around which conversations it can read and answer. Design that boundary before granting access. Also decide who notices a sleeping or disconnected host and what the application tells a user while the bridge is unavailable.
A different comparison
Do not score this installation as though it includes a provisioned business number and commercial support commitment. It may be useful for a controlled technical experiment where the operator accepts maintenance. The linked installation guide supports the operating model; it is not evidence that we have deployed and load-tested a production agent on it.