The Open Data movement is a fairly recent phenomenon. The main idea is that public data gathered, maintained and used by public organizations, should be made available for access and re-use to citizens and companies. Initially born in Anglo-Saxon countries, it is spreading to all western democracies. It has several facets: legal, economic, technological, political, etc. In this presentation, we will address all these issues with key actors from the field. We will also relate Open Data to Open Source.