Casio, Leica, Pentax, and Ricoh generate DNG files in camera but did not require permission from Adobe to do so (nor any patent licensing, nor any money changing hands, etc.). Occasionally they may ask us some questions or ask us to verify compatibility, check recommended settings, etc.
Pentax used to offer a choice between their own PEF format and DNG, but dropped PEF in their latest models. There remains vendor-specific and proprietary information in the private MakerNotes, which is fine. That is, DNG supports private MakerNotes so Pentax actually just embeds the same private metadata in their DNG that they used to embed in their PEF.
Vendors who want to provide private or model-specific metadata like focus point information, or focus position metadata, or body orientation (e.g., roll, pitch) can easily do so with DNG, and the vendors listed above are already doing so. In some cases, their own software is able to report additional information to the user or perform image processing functions using this private metadata, that Adobe software does not (this is private data, after all).
Ultimately there is an important distinction between the ability to (1) read a raw image, and (2) process and/or interpret the raw image & metadata. DNG as a file format is really only concerned with #1, though it does have some optional tags for assisting with #2. In other words, different vendors may have different preferred appearances and different features (e.g., focus point display) -- which falls under #2 -- but none of that should prevent you from fundamentally reading the image (#1).