OpenCV is free for commercial or research use, and we have the same policy on the code examples in the book. Use them at will for homework, for research, or for commercial products. We would very much appreciate referencing this book when you do, but it is not required. Other than how it helped with your homework projects (which is best kept a secret), we would like to hear how you are using computer vision for academic research, teaching courses, and in commercial products when you do use OpenCV to help you. Again, not required, but you are always invited to drop us a line.