Never heard of them. Kellnr is already three years old. It started when only git was supported as the registry protocol. I later added the sparse (http) registry API. Just a few weeks ago, I removed the old git API, as sparse seems established as the new standard. I never thought about namespacing, as Kellnr is aimed as private hosting for individuals or companies, where name squatting isn't an issue. But theoretically, I could add that.