Moodle does not need a subscription. Every part of the software required to run it is open source and free to use.
However running a Moodle site does have a cost. Either you pay for someone else's knowledge and time or you invest the time to learn how to set up and run Moodle yourself.
The cost of an internet accessible Moodle can be as low as $5 a month. It depends on you. Is your time or your money more valuable?
Back to the Mac. The machine running Moodle must have an internet address if remote access is required. That would need internet hosting.