This licence from Adobe covers copying the files in
libs/dngwriter/extra/dng_sdk

It is a non-copyleft free software license, compatible with the GNU
GPL.

The documentation clauses are non-free but no relevant documentation
is included.

It was downloaded from 
https://www.adobe.com/support/downloads/dng/dng_sdk_eula_win.html

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DNG SDK License Agreement

NOTICE TO USER:

 Adobe Systems Incorporated provides the Software and Documentation
 for use under the terms of this Agreement. Any download,
 installation, use, reproduction, modification or distribution of the
 Software or Documentation, or any derivatives or portions thereof,
 constitutes your acceptance of this Agreement.

 As used in this Agreement, "Adobe" means Adobe Systems
 Incorporated. "Software" means the software code, in any format,
 including sample code and source code, accompanying this
 Agreement. "Documentation" means the documents, specifications and
 all other items accompanying this Agreement other than the Software.

1. LICENSE GRANT

 Software License.  Subject to the restrictions below and other terms
 of this Agreement, Adobe hereby grants you a non-exclusive,
 worldwide, royalty free license to use, reproduce, prepare derivative
 works from, publicly display, publicly perform, distribute and
 sublicense the Software for any purpose.

 Document License.  Subject to the terms of this Agreement, Adobe
 hereby grants you a non-exclusive, worldwide, royalty free license to
 make a limited number of copies of the Documentation for your
 development purposes and to publicly display, publicly perform and
 distribute such copies.  You may not modify the Documentation.

2. RESTRICTIONS AND OWNERSHIP

 You will not remove any copyright or other notice included in the Software or Documentation and you will include such notices in any copies of the Software that you distribute in human-readable format. 

 You will not copy, use, display, modify or distribute the Software or
 Documentation in any manner not permitted by this Agreement. No title
 to the intellectual property in the Software or Documentation is
 transferred to you under the terms of this Agreement. You do not
 acquire any rights to the Software or the Documentation except as
 expressly set forth in this Agreement. All rights not granted are
 reserved by Adobe.

3. DISCLAIMER OF WARRANTY

 ADOBE PROVIDES THE SOFTWARE AND DOCUMENTATION ONLY ON AN "AS IS"
 BASIS WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, EITHER EXPRESS OR
 IMPLIED, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OR CONDITIONS OF
 TITLE, NON-INFRINGEMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR
 PURPOSE. ADOBE MAKES NO WARRANTY THAT THE SOFTWARE OR DOCUMENTATION
 WILL BE ERROR-FREE. To the extent permissible, any warranties that
 are not and cannot be excluded by the foregoing are limited to ninety
 (90) days.

4. LIMITATION OF LIABILITY

 ADOBE AND ITS SUPPLIERS SHALL NOT BE LIABLE FOR LOSS OR DAMAGE
 ARISING OUT OF THIS AGREEMENT OR FROM THE USE OF THE SOFTWARE OR
 DOCUMENTATION. IN NO EVENT WILL ADOBE BE LIABLE TO YOU OR ANY THIRD
 PARTY FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, INCIDENTAL, OR SPECIAL
 DAMAGES INCLUDING LOST PROFITS, LOST SAVINGS, COSTS, FEES, OR
 EXPENSES OF ANY KIND ARISING OUT OF ANY PROVISION OF THIS AGREEMENT
 OR THE USE OR THE INABILITY TO USE THE SOFTWARE OR DOCUMENTATION,
 HOWEVER CAUSED AND UNDER ANY THEORY OF LIABILITY, WHETHER IN
 CONTRACT, STRICT LIABILITY OR TORT (INCLUDING NEGLIGENCE OR
 OTHERWISE), EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 DAMAGES. ADOBE'S AGGREGATE LIABILITY AND THAT OF ITS SUPPLIERS UNDER
 OR IN CONNECTION WITH THIS AGREEMENT SHALL BE LIMITED TO THE AMOUNT
 PAID BY YOU FOR THE SOFTWARE AND DOCUMENTATION.

5. INDEMNIFICATION

 If you choose to distribute the Software in a commercial product, you
 do so with the understanding that you agree to defend, indemnify and
 hold harmless Adobe against any losses, damages and costs arising
 from the claims, lawsuits or other legal actions arising out of such
 distribution.

6. TRADEMARK USAGE

 Adobe and the DNG logo are the trademarks or registered trademarks of
 Adobe Systems Incorporated in the United States and other
 countries. Such trademarks may not be used to endorse or promote any
 product unless expressly permitted under separate agreement with
 Adobe. For information on how to license the DNG logo please go to
 www.adobe.com.

7. TERM

 Your rights under this Agreement shall terminate if you fail to
 comply with any of the material terms or conditions of this
 Agreement. If all your rights under this Agreement terminate, you
 will immediately cease use and distribution of the Software and
 Documentation.

8. GOVERNING LAW AND JURISDICTION. 

 This Agreement is governed by the statutes and laws of the State of
 California, without regard to the conflicts of law principles
 thereof. The federal and state courts located in Santa Clara County,
 California, USA, will have non-exclusive jurisdiction over any
 dispute arising out of this Agreement.

9. GENERAL

 This Agreement supersedes any prior agreement, oral or written,
 between Adobe and you with respect to the licensing to you of the
 Software and Documentation. No variation of the terms of this
 Agreement will be enforceable against Adobe unless Adobe gives its
 express consent in writing signed by an authorized signatory of
 Adobe. If any part of this Agreement is found void and unenforceable,
 it will not affect the validity of the balance of the Agreement,
 which shall remain valid and enforceable according to its terms.
