Leider, leider lautet die Antwort schlicht und einfach: nein.
Daher sehe ich ziemlich schwarz, bald mal mit anderen Leuten GBA zu spielen, ohne mehrere GBAs und Spiele sowie ein Linkkabel zu kaufen. Ich würde auch gerne mal GBA-Spiele mit 2-4 Leuten zocken, aber der einzige Emulator, bei dem das geht, ist der NO$GBA, dessen Entwicklung allerdings, wie beim NO$GMB, eingestellt wurde, weil die Registrationskeys im Internet und sonst wie vervielfältigt wurden, und sich daher die Kompatibilität zu den Roms auf sehr tiefer Ebene befindet. Echt schade, wirklich...Folgendes steht in der FAQ auf der HP vom VBA:
Why don't you add link?
Link sounds great but it is far more difficult than most people think.
Often users will mention that Snes9x (or other emulators) have link support, so it shouldn't be hard to add it to the emulator.
Truth is that SNES (and any other console) are completely different than handhelds. Let's compare:
console - a console normally supports multiplayer by nature: you can plug multiple controllers and have several people share the same console and play together. One console, one cartridge, multiple players.
handheld - handhelds are designed for single player on a single unit. To achieve multiplayer, a link cable is needed. This allows the different units to communicate and achieve the multiplayer effect. Multiple units linked together, multiple players.
On the console case, it is easier to add multiplayer because you can just link two instances of the emulator and only send the keys of each player. They don't have any communications feature by nature.
Handhelds on the other hand have built-in communication features which allow full speed communication between units. This is a lot harder to emulate: it requires a full connection between two emulators which need to be correctly synchronized or nothing works. It is a lot harder to achieve.
Will link ever be supported?
For the time being, I've decided not to add link support. The reason is that link would increase the interest in the emulator by users using illegal copies of software.
Why don't you use Kaillera or look at TGB Dual?
Kaillera is used for machines that support multiple players in one machine, for example normal consoles like Playstation, N64, GameCube, Genesis, etc... It works by connecting the players through the Internet and only exchanging their joypad movements. That makes your computer think there is another person playing with you locally.
TGB Dual emulates two CPUs to get linking working: one where you actually see the screen and a hidden one used to communicate with the remote player. The data transmitted is in the same way as in Kaillera. Some other steps are taken to transfer save states, etc but it is not a true GB Link cable emulation.
The GBA Link cable can send data up to 2Mb/s which is really a lot of data and considering how the GBA emulation requires a fast computer, it would require a really fast computer to achieve a decent emulation. It would be possible to take the TGB Dual approach but that would require a really fast computer. For the time being, I will not add link as mentioned a million times.]