Leica did release the Digital Module R for Leica R SLR. And as a good student, they use DNG and don't even provide their own proprietary software for them, but just a third party proprietary software: Adobe's.

Someone even posted sample files. One still have to check how good Leica developer support is towards helping development, but at least they get the start right by not using another undocumented file format. If only they could document previous RAW files they did release ?

Concerning DNG it is not an Open file format, as it is owned by Adobe, like PDF, but it is completely documented, free (of charge) to use as is, and it does not prevent any Free Software implementation from the documentation.