If I remember watching the screen I don’t think this was a looping video, but being that this was developed by Roku themselves I would assume this is coded at the core of the device (like Brightscript is) or done in the NDK as Roku would obviously have free access to it. I would be extremely surprised if this was done in Brightscript.
This has been discussed multiple times. If I remember correctly they didn’t develop it; they got it from someone else, but I can’t remember the details. It wasn’t originally developed for the Roku platform. Someone posted the developer way back when, but I can’t find it now.