Just the implementation and mine does not require Calibre (I know the plugin can be used without Calibre, but it is not its primary use case).

No acsm. It’s books protected by Adobe DRM.

Not right now, but I will see if I can figure something out.

Yeah. Specify the books by url. Just run audiobook-dl [url] after installing. It supports downloading multiple books with a single command.

Just implemented it in audiobook-dl. Hope it works.