"In my opinion Calibre is a marvelous tool but is too big and has too much dependencies to be used for its content server. That's the main reason why I coded this OPDS server. I needed a simple tool to be installed on a small server (Seagate Dockstar in my case).
I initially thought of Calibre2OPDS but as it generate static file no search was possible.
Later I added an simple HTML catalog that should be usable on my Kobo.
So COPS's main advantages are :