what is the patent status of surf/sift

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When I search google (et al.) for patent status, I do not get a clear answer. Building with the current release produces this runtime error:

terminate called after throwing an instance of 'cv::Exception' what(): OpenCV(4.2.0) /mnt1/build5/cinelerra-5.1/thirdparty/opencv_contrib/modules/xfeatures2d/src/sift.cpp:1208: error: (-213:The function/feature is not implemented) This algorithm is patented and is excluded in this configuration; Set OPENCV_ENABLE_NONFREE CMake option and rebuild the library in function 'create'

Is a release in the works without this restriction, or are the patents still in force?

gg