[andersonfreitas]

SIFT is patented. SURF is a similar and alternative method to SIFT.

[jboy]

SIFT and SURF are both patented in the US.

SIFT: http://www.google.com/patents/US6711293

SURF: http://worldwide.espacenet.com/publicationDetails/biblio?CC=...

More info: http://opencv-users.1802565.n2.nabble.com/SURF-protected-by-...