@nirik: calibre expects either that the disks are always mounted before calibre tries to mount them or that calibre-mount-helper mounts them.
I seriously doubt you can guarantee that the disk will always be mounted, therefore if you don't want to ship calibre-mount-helper, then you should replace it with a shell script that does the mounting/ejecting. Otherwise, you cripple calibre functionality and I get to deal with the bug reports.
Notice to all: I can not
provide assistance with DRM removal, for legal reasons, so please do not contact me about it.