SIFT and SURF are both patented in the US. SIFT: http://www.google.com/patents/US6711293 http://www.google.com/patents/US6711293 SURF: http://worldwide.espace

SIFT and SURF are both patented in the US. SIFT: http://www.google.com/patents/US6711293 http://www.google.com/patents/US6711293 SURF: http://worldwide.espacenet.com/publicationDetails/biblio?CC=US&NR=2009238460&KC=&FT=E&locale=en_EP http://worldwide.espacenet.com/publicationDetails/biblio?CC=... More info: http://opencv-users.1802565.n2.nabble.com/SURF-protected-by-patent-tp3458734p3463927.html http://opencv-users.1802565.n2.nabble.com/SURF-protected-by-...