JustePort itself supports only MPEG4 Apple Lossless (.m4a) files as input, but since the RSA encryption key used is now available, it is easy to develop full-featured third-party streaming clients for AirPort.
Earlier this year Johansen developed PlayFair (now known as Hymn), which removed the DRM wrapping from songs sold at the iTunes Music Store. Last month he released FairKeys, which lets iTMS users to extract FairPlay keys from Apple's servers. The keys are required to authenticate computers to play songs purchased from iTMS.
More information on JustePort is available at Jon Lech Johansen's blog which at the time of writing is suffering from major slashdot slowdown.
Source: The Register