As far as I understand, both SURF and SIFT are patent protected. Are there any alternative methods that can be used in a commercial application freely? For more info on the patent check out: http://opencv-users.1802565.n2.nabble.com/SURF-protected-by-patent-td3458734.html
![What are some free alternatives to SIFT/ SURF that can be used in commercial applications?](https://cdn-ak-scissors.b.st-hatena.com/image/square/7ff1ba5492c2fd18a9f0dfcccd0aa11807524aff/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Fdsp%2FImg%2Fapple-touch-icon%402.png%3Fv%3De0439310c223)