The focus of BibServer is displaying collections. The function of curating a collection, or managing access to a collection, is achievable via off-site methods. For example, if your collection is a BibTex file, just edit it as you see fit and upload your file whenever you have made changes. You can therefore control the editing process by controlling access to that source file however you see fit.
Eventually we will enable creating and editing collections directly on BibServer – but this is secondary functionality.