OpenCV is described as '(Open Source Computer Vision) is a library of programming functions for real time computer vision' and is an app in the development category. There are seven alternatives to OpenCV for a variety of platforms, including Windows, Linux, Android, Mac and Chrome OS. The best alternative is SimpleCV, which is both free and Open Source. Other great apps like OpenCV are Accord.NET Framework, libdwt, BoofCV and ImageUltimate.
SimpleCV is a Python interface to several powerful open source computer vision libraries in a single convenient package. With it, your software can have access to high level algorithms in feature detection, filtering, and pattern recognition in a unified framework.
BoofCV is an open source library written from scratch for real-time computer vision. Its functionality includes, low-level image processing, camera calibration, feature detection/tracking, structure-from-motion, fiducial detection, and recognition.