Licence proliferation continues to be a major challenge for open data. When licensors decide to create custom licences instead of using standard open licences, it creates a number of problems. Users of open data may find it difficult and cumbersome to understand all legal arrangements. More importantly though, legal uncertainties and compatibility issues with many different licenses can have chilling effects on the reuse of data. This can create ‘data use silos’, a situation where users are legally allowed to only combine some data with one another, as most data would be legally impossible to use under the same terms. The ever-growing complexity of our licensing landscape may support such silos – counteracting efforts like the European Digital Single Market strategy, preventing the free flow of (public sector) information and impeding the growth of data economies. Standardised licences can smoothen this process by clearly stating usage rights. This report outlines the problems of an ever-growing complexity of open licences, the risk of data use silos, and explains why reusable standard licences, or putting the data in the public domain are the best options for governments. While the report has a focus on government, many of the recommendations can also apply to public sector bodies as well as publishers of works more broadly.