Business-to-government (B2G) information sharing can benefit government organisations, as well as businesses. Yet, businesses are often reluctant to share, as data sharing might not just provide benefits but also entails risks. Therefore, a system supporting B2G information sharing should provide the appropriate level of openness, such that the advantages of openness and possibilities to control risks for businesses are balanced. At the same time, the information obtained by the government should be useful. We identified three architectural layers at which B2G information sharing architectures can have different levels of openness, viz. the Software Layer, the Access Control Layer and the Data Layer. In this work, we compare three archetypical configurations of architectures for B2G information sharing with different levels of openness. Our aim is to provide insight into their impact on the possibilities for obtaining advantages from information sharing and managing risks of opening up data. We found that the relationship between the different levels of openness and the advantages and risks of information sharing is highly complex. We discuss this complexity and find that different levels of openness are appropriate in different situations.