ProRes 422 is Apple's lossy video high quality video compression format. It is the native format of Apple's popular Final Cut Pro video editing software. ProRes is also the format requested for HD Television and HD and SD Film to be delivered to the iTunes Store.
Apple favors its own OS X when releasing the ProRes. Apple updated the ProRes decoder for Mac OS X in June 2011, and Final Cut Pro X only for Macintosh provides a 64-bit ProRes implementation. The Windows download is 32-bit only and stuck in 2008 (not to mention the sorry state of QuickTime for Windows in general), and there is no ProRes decoder for Linux despite the growing cloud transcoding industry. Some Linux users have even resorted to loading a Windows DLL into MPlayer and Mencoder to handle ProRes content. There do appear to be a small handful of third party products that by hook or by crook include ProRes support.
Still Apple products and tools are the only first class citizens of the ProRes ecosystem or were until now. Today an intrepid hacker released an open source reverse engineered ProRes decoder for FFmpeg. Now everyone trying ingest ProRes files is on an equal footing. The iTunes Store's unfair ingestion advantage over Hulu, Netflix, YouTube, and the cloud transcoding industry is over. The days of loading a 32-bit Windows DLL are over. ProRes can now be decoded on ARM, in a 64-bit process, or on any platform with a C compiler. Hopefully someday this decoder will be extended into an encoder as well to end Apple's advantage in authoring ProRes not just consuming it.
These opinions are strictly mine and not those of my employer (YouTube).