Issue 16736

[saskatchewancatch]

relates opencv/opencv#16736

Move SIFT out of non-free into free. I emailed David Lowe the author of SIFT and he mentioned that there is no possibility for patent extension. So this should be safe to go into free.

Build tested on Win64/VS15 with docs. SIFT tests complete when make is configured without non-free enabled.

Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

• I agree to contribute to the project under OpenCV (BSD) License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or other license that is incompatible with OpenCV
• The PR is proposed to proper branch
• There is reference to original bug report and related work
• There is accuracy test, performance test and test data in opencv_extra repository, if applicable
  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

[alalek]

Thank you 👍

[AlucardNosferatu]

A big good news, looking forward to SIFT in 4.x

[ayush111111]

Thank you !!