The document discusses mashups and how Creative Commons licenses enable them by lowering barriers across organizational, technical, and legal boundaries. It defines mashups as the reuse of digital bits, content, or media from multiple sources to create a new work. Interesting mashups cross different boundaries, and commons licenses promote this by making permission implicit. To be good "mashup citizens," creators should use open standards and license their works with permissive terms like Creative Commons licenses to allow others to build upon their work.