‘Open data’ refers to the idea that all public data should be freely available for use and reuse by others, unless restrictions apply e.g. for protection of personal data.

Reference Doc: Revised EIF

Open source is a term describing a means of developing and distributing software that ensures software is available for use, modification, and redistribution by anyone. Generally, anyone can download open source software for little or no cost, and can use, share, borrow, or change it without restriction.

In the context of interoperable public services, the concept of openness mainly relates to data, specifications and software.

Reference Doc: Revised EIF

Organisational interoperability refers to the way in which public administrations align their business processes, responsibilities and expectations to achieve commonly agreed and mutually beneficial goals. In practice, organisational interoperability means documenting and integrating or aligning business processes and relevant information exchanged.