I started image processing with OpenCV as a hobby.
Now that the SIFT patent has expired (source: US6711293B1 - Method and apparatus for identifying scale invariant features in an image and use of same for locating an object in an image - Google Patents), SIFT can be implemented in OpenCV. Therefore, based on the fact that the OpenCV license is 3-clause BSD and Apache 2 (source: https://opencv.org/license/), I’m thinking that commercial and academic use may be possible. Is there any money involved for commercial use and academic use?
As I understand it, no. Expired patents become public domain. That is the bargain the patent applicant/holder entered when they filed it.
If you google for “sift patent” and “patent expiration”, you’ll find all the discussion you’ll need.
As for the licenses on the library: they are those licenses. They don’t talk about fees, so there are none.
I am not a lawyer. This is not legal advice.
Thank you for your answer.
It was a very easy-to-understand answer. So, unlike SIFT, whose patent has expired, is it correct to understand that the SURF algorithm in opencv_contrib may incur costs due to patent issues?
Depends on what patents exist, what they cover, and whether they’ve expired. So far, it looks like the algorithm itself has no patent, but it has a license, and there are patents on applications of the algorithm.
Everything depends on what licenses exist, or what licensing you could negotiate.