Is an active protocol required to move media (content) files, or is it enough to simply transfer the media files, e.g., over a Marlin-agnostic memory card/USB stick between devices?
No active protocol is necessary for content bound to a user. If the content is device-bound, as is the case for Broadcast content that signaled Copy One Generation during delivery, then the License Transfer protocol is required. (Copy One Generation is a broadcast Copy Control Information attribute indicating that the content can only be played on a single device.