Processing is a flexible software sketchbook and a language for learning how to code within the context of the visual arts. Developed by Casey Reas, Ben Fry, and many others: http://www.processing.org/about/people.html
License: Open Source
OpenFrameworks is a C++ library that provides more control and flexibility, making it suitable for advanced programming and complex projects, while Processing, with its user-friendly syntax and rapid prototyping capabilities, is better suited for artists and designers looking to create visual projects quickly.