Apple Lossless Audio Codec (ALAC) was developed by Apple to deliver lossless audio compression, with the data being stored in an MP4 container. The format was open-sourced by Apple in 2011.
ALAC-encoded files are playable using Apple's iTunes media player. Applications using the open-source libavcodec can also playback and otherwise manipulate ALAC-encoded files. For a list of such applications, see here.
Windows and MacOS PowerPC compiles of the reverse-engineered ALAC decoder v0.1.3 can be found here