That's correct. There will be no centralized website. You will have to run a Synereo node to take part in the network. The plan is to make running a Synereo node as easy as downloading, installing, and running an app. You log in to your account via the app.
Is this definitely the way it will work - you will have to download and install an app to be on the Social Network? I assumed various individuals could host their own nodes and you could register there. Having to download/install something to get connected seems like a fairly large barrier to entry
You'll be able to do that too, but the goal is to have as many people as possible running their own node as it aids decentralization.