I think most folks miss out on the fact that Apple uses open source within the OS. From the printer drivers, to the compilers and scripting languages are all the key underpinnings of the utilizes around the OS. Also Apple has funded huge improvements and interesting new features to GCC and especially LLVM compilers. Of course they are not along here: Intel, AMD, Red Hat, SuSE, Ubuntu, nVidia, Oracle and Google have all contributed and all offer propriety products and solutions. (SuSE has a licensing deal with Microsoft as well, great way to get funded i guess).
I would assume open sourcing ALAC is probably one of the first step to open source h.264, which is another codec that isn't actively requiring folks to license, but not exactly open source.