Provided you are attributing the work of the OpenCV project to the OpenCV project, and your own work to yourself, you are free to do just about whatever you want under the BSD license. You could for example distribute proprietary binaries containing code you did not author, or if you wanted, you could release your derivative source. With the GPL, all derivative works must be accompanied by source. More detail here:
http://en.wikipedia.org/wiki/Free_so...yleft_opinions