I had a similar question. After a bit of perusing, it isn't immediately clear (especially since the install page just has a message saying it's not yet available to the public). But the following FAQ seems to suggest that it will run directly on the TV:
>Can I run Plasma Bigscreen on my TV or setup-box?
>In theory, yes. In practice, it depends.
>Hardware support is not dictated by Plasma Bigscreen, instead it depends on the devices supported by the distributions shipping it. See the install page for more details of distributions shipping Plasma Bigscreen.