Your assumption is quite wrong, and I think you've already been told so by Jeff, probably 3 or 4 times, somewhere earlier in the thread. There is no licensing, and no tie to the SDK. At most, someone might want to read publicly-available documentation.
Sorry, John. I did read the links Jeff posted.
First one on DNG support: http://www.barrypearson.co.uk/articles/dng/products_y6.htm
Following some of the links in the article, which discussed licensinghttp://www.barrypearson.co.uk/articles/dng/commentary1.htm
"Adobe have published a royalty-free license for anyone to develop and supply products using the DNG specification. Adobe have released a freely-available (optional) SDK, and a royalty-free license for anyone to use it."
This linked me to: http://www.adobe.com/products/photoshop/extend.displayTab2.html
Where in one section it said:
'Digital Negative (DNG) Specification Patent License
Adobe is the publisher of the Digital Negative (DNG) Specification describing an image file format for storing camera raw information used in a wide range of hardware and software. Adobe provides the DNG Specification to the public for the purpose of encouraging implementation of this file format in a compliant manner. This document is a patent license granted by Adobe to individuals and organizations that desire to develop, market, and/or distribute hardware and software that reads and/or writes image files compliant with the DNG Specification.'
Adobe may revoke the rights granted above to any individual or organizational licensee in the event that such licensee or its affiliates brings any patent action against Adobe or its affiliates related to the reading or writing of files that comply with the DNG Specification."
OK...well it is a broad based license, but it is a license, unless I read it wrong, which is not impossible ;-)
In the last article it also mentioned:
The DNG SDK provides support for reading and writing DNG files as well as for converting DNG data to a format that is easily displayed or processed by imaging applications. This SDK can serve as a starting point for the addition of DNG support to existing applications that use and manipulate images or as an aid to the inclusion of DNG support within cameras."
"DNG Codec for Windows
The DNG Codec provides a method for Windows 7 customers to view DNG files in the Windows Explorer and Photo Gallery."
So it seemed to me that read/writing to the files was via the SDK. I was not aware that any of the viewers or other applications had implemented the own code to read the DNG files. However, I believe that they are still contained within the license.