Open data provides public data in open formats for free reuse, but data reuse is still low because building services from open data is difficult. While open data is a start, true business opportunities require open information systems that provide real-time data access through APIs. For example, the iCity project opens city information systems in a standardized way to allow third parties to easily develop new services on top of the data. Open information systems, not just open data, are needed to transform opportunities for businesses.