This document summarizes open data definitions and licensing models. It discusses what open data is, including that it is a model to extract value from public sector information by using data to build new tools and services. Open data refers to data that can be freely used, modified, and shared by anyone for any purpose. The document outlines several open data definitions and principles, including from the Open Knowledge Foundation and their Open Definition. It also discusses open data licensing models and provides examples of open government data programs from countries like the US, UK, and Australia.