No, the products WinForm HMI, Web HMI, WPF HMI, .NET Data Connector, Recipe Connector, and Excel Connector will all have the ability on their own to write to OPC Servers when a write occurs. The Data Source of the Tag will determine where the value will be written.
Yes, by installing the OAS Service at the data source and the destination the values can be setup to automatically transfer remotely. At the destination set the Data Source of the Value as Tag and set define the data source tag Value, then in the Target tab defines either a local OPC Item or a local or remote Open Automation Software Tag if using a Driver Interface Tag as a destination.
If transferring values directly to OPC Items, yes.
If transferring values to remote Open Automation Software tags you only need a license on the source where the Target is being defined.
Yes, the following Driver Interfaces are incorporated directly into Open Automation Software: