Those files are run by the quake engine (i.e. your urban terror game). This is because when you record a demo, your not actually recording video, but the communication the server is sending back to the player at the time of demo. This is why you can adjust your settings for demo playback, but also why you need those (urt) game elements for playback.
Theoretically if you can run urt on your phone you should be able to play demos, but that is another can of worms (maybe some type of linux mobile). To my knowledge there is no stripped down media/demo player for urt, everything out there plays demos from the actual game engine.