Only repositories for which you have admin permissions will appear on the repository registration page and only those repositories can be registered. The reason for this is GitHub/Bitbucket requires admin permissions to add an SSH key to the repository. And that SSH key is required by Loadroid to checkout code, and also to add a webhook, so GitHub/Bitbucket tells Loadroid each time new code is pushed.
However, once the repository is registered by an admin, users who don't have admin permissions (i.e users with read/write permissions) will also be able to view the registered repository on the tests page.
Users who do not have read/write/admin permissions to the repository on GitHub/Bitbucket, cannot access to any information about the repository on Loadroid.