The Guardian Open Platform is the suite of services that make it possible for us to build applications with the Guardian. They have opened up their platform so that everyone can benefit from the journalism, the brand, and the technologies that power guardian.co.uk. The Open Platform currently includes two products, the Content API and the Data Store.
1. The Content API is a mechanism for getting Guardian content. You can query their content database for articles and get them back in formats that are geared toward integration with other internet applications. The Content API is a free service including commercial applications. However, there are some limits and restrictions.
2. The Data Store is a collection of important and high quality data sets curated by Guardian journalists. You can find useful data there, download it, and integrate it with other internet applications. The Data Store has a range of different uses for different types of partners. They will include relevant terms and conditions along with each service.
The Guardian Open Platform is a useful environment for anyone who creates for the internet. They will offer more services in the future such as an ad network and an application platform.
Source: The Guardian Open Platform