Looks to be a custom UI using the 2D APIs. The developer is listed as "Float Left Interactive" (i.e., not Roku) so it's unlikely that Roku would be able to release the source.
My Channels: http://roku.permanence.com - Twitter: @TheEndlessDev
Instant Watch Browser (NetflixIWB), Aquarium Screensaver (AQUARIUM), Clever Clocks Screensaver (CLEVERCLOCKS), iTunes Podcasts (ITPC), My Channels (MYCHANNELS)
