What is the difference between Merlin Project and Merlin Server?
Merlin Server is an add-on to the basic software Merlin Project.
You work with Merlin Project on your local Mac. Your projects are generated and maintained there. Whenever you like to work at the same time or together with others (project members or devices), you may use Merlin Server. Merlin Server is a separate product which has to be installed on a Mac of yours. It is no cloud service.
How does Merlin Server work exactly?
Publish your project via Merlin Server. Other project members or devices can then subscribe to that project - e. g. with Merlin Project Go on the iPhone or iPad. The project file will be loaded on your device and also only modified there.
Whenever this device is connected to the internet, the local Merlin Project will try to communicate with Merlin Server, in order to synchronize modifications.
You do not have to do anything special to sync changes, it all happens in the background. In case you are offline, Merlin Project will wait patiently until you are back online to sync the latest changes.