Website MacRumors is reporting that developer James Laird was able to reverse engineer the Airport Express key and posted an open source emulator he named Shareport. This opens up Airport Express emulation to people other than Apple or licensed third parties.
According to the description, it emulates Airport Express to allow users to stream music from their iTunes library and other compatible devices.
One report says that before it was only possible for users to stream from iTunes or licensed third-party software/hardware to AirPort Express. Now users can do it the other way around, that is stream iTunes to third-party party software or hardware.
This could make it possible to stream content easily between devices around the home that typically wouldn't be capable of such things. As MacRumors puts it, this could mean other Macs, modified consoles or other mobile devices with an application designed for this.
We can be sure that Apple is not thrilled with this news. Just as long as they don't start taking the Sony route, [ed. note: Looks like news of this case being settled just came out today.] it's all good.