While it does seem to be regarded to be easy to avoid infringing on the SIFT patent by changing the algorithm in a minor way (e.g. using SURF features but doing

While it does seem to be regarded to be easy to avoid infringing on the SIFT patent by changing the algorithm in a minor way (e.g. using SURF features but doing SIFT-style search), I know there are companies that have licensed SIFT from Lowe, and I would expect he's been paid for those licenses.