That section is intended to cover basic operation of the service. The first line declares that you retain ownership of your content. In order to use Plex features like uploading photos from your home computer and seeing them on your mobile device, Plex needs the right to access and copy that content in order to make everything work.
For example, when you playback a video on your iPhone there’s a few things that need to happen. We need the right to create a copy of the video that exists on your Plex Media Server, the right to create a derivative work if it’s transcoded, and the right to transmit it to your iPhone.
This paragraph is largely a carryover from our previous terms of service which were in place for nearly three years. We did notice that the “limited purpose” qualifier was removed and we’ll work with our lawyers ASAP to make make this even clearer.
