actually, the link possibility is established, the only problem is, you can't load games on the second screen and when starting the game can't get past your first fight because thanks to some sort of strange reason you need sound to end the fight and you don't have it, but if you want to try it, there are some tutors on internet, Search "NO$GBA link diamond" up on google and have a look arround, you'll eventually find out how, but again, you won't be able to pass the first battle because at the end of the battle the sound must work... So I guess, as ******d up as it is we have to wait a few versions until this will be fixed, unless you can program yourself !
That's nonsense and those people pretending it works are phonies.
The problem is not that you can't start two games, the problem is that no WiFi transfer of any sort is possible. In other words even if you could get Diamond and Pearl to run perfectly alongside each other it would still not help as they can't communicate with each other. Now don't come and tell me that no$gba has basic WiFi support, because that means nothing, in fact there's an asterisk right next to that point which further down the page explains that it has no practical use whatsoever so far, it even fails sending packets in Pictochat. Now I would think the guy that made the emu would know a little more about the limitations of it's features than a random bunch of pokenerds on the net.
Also it's not strange that when sound is off Pokemon can't proceed as in no$gba setting sound to none does not just mute the sound, it removes the emulation of sound entirely. Now Pokemon waits for the battle cry of the defeated Pokemon, but as sound is not emulated that never happens and so the game simply waits forever and appears frozen eventhough it's just waiting for something before it would keep on running.