Molecular biology data are subject to terms of use that vary widely between databases and curating institutions. This research presents a taxonomy of contractual and technical restrictions applicable to databases in life science. It builds upon research led by Science Commons demonstrating why open data and the freedom to integrate facilitate innovation and how this openness can be achieved. The taxonomy describes technical and legal restrictions applicable to life science databases, and its metadata have been used to assess terms of use of databases hosted by Life Science Resource Name (LSRN) Schema. While a few public domain policies are standardized, most terms of use are not harmonized, difficult to understand and impose controls that prevent others from effectively reusing data. Identifying a small number of restrictions allows one to quickly appreciate which databases are open. A checklist for data openness is proposed in order to assist database curators who wish to make their ...