Actually, from the look of it, there appears to be many different things going on.
The first site appears to be taking a feed found elsewhere and tacking on a opening clip to advertise themselves with some of the "network OTA broadcasters" like CBS 2 Chicago is really resolving to the actual feed from CBS 2 when they do news and then cuts off when they aren't, the difference, is that you are using the interface they provide instead of the direct link. Not all of them are like that, there is obviously some retransmissions going on with other things like cable networks and such require add-ons from P2P streaming sites, which are basically at home illegally streaming local tv to the net (alot of this can be seen if you look up Peer to Peer streaming video links)
They seems to be not much more than a collection of links to the streams, I used to have time to look up links to radio stations and tv station streams (both legit and not-so-legit) but not currently. It is almost like when you look up streaming radio links on radio-locator or other such list site,they just have the idea that they can collect more ad revenue by tossing the streams into thier own interface and whatnot.
I'd check the TVU thing out, but I'm not about to install it on my machine, there's a bunch of those platform based applications that connect to a list-serv site and make the whole thing look user-friendly, but in truth, there's alot of dead links out there, and many "wild-feed" type links that, like the above CBS 2 example, only stream the local news and are unavailable most of the day.