The phrase "open registry" refers to a public database or record of information that is freely accessible and can be viewed or used by anyone. Full definition
If you want to show the account again, open the registry editor and change the value for the user name on the right that you want to show again to 1. (howtogeek.com)
To take ownership of a registry key, open the registry editor, if it is not already open. (howtogeek.com)
The American Kennel Club has established a genetics foundation to pursue such research, and the University of California Davis has spawned the Institute for Genetic Disease Control to provide open registries for genetic problems. (canismajor.com)