Yes, you can install YouTube (I can't remember if it is already installed out of the box) from Google Play store. But please do not install anything without asking us. We just released Omnia S1 and quite busy with several product releases this month (AMG STA, AMG PRE, SW-8, WR-1, Hi mDAC). This is crazy, never happened before.
Once we get over this busy month, we will have time to prepare usage guides and other enhancement for Omnia S1.
Currently you have to connect S1 to a monitor, bluetooth keyboard and mouse to use it (you can remove them after configuration if it is just being used as music server since the admin page can be accessed remotely).