i Tunesi recent Apple Lossless Audio Codec (ALAC) encoding option has always had a catch: only iTunes, QuickTime-supported systems, and iPods can read the format. David Hammerton, however, has released the first version of a basic decoder that allows other systems and players to recognize the files.
Only a decoder is currently offered, but Hammerton notes that writing an encoder should be fairly easy. Additionally, his decoder only handles mono and stereo ALAC files--ALAC itself can support up to 8 channels. Like the encoder, Hammerton says adding support for multiple channels should be "trivial."
Hydrogenaudio is offering a rather extensive discussion on the decoder, as are countless posters on Slashdot.