You can access much of Calibre’s functionality via its command-line interface. Should be easy to make a script for DRM-removal or conversion (for conversion there’s also pandoc). And the viewer can be started as a separate program, or other document viewers (like Okular on Linux) can be used.
Also, Callibre has lots of ways to customize the UI or disabling functionality via the plugin system. You can probably turn off most things you don’t use.
You can access much of Calibre’s functionality via its command-line interface. Should be easy to make a script for DRM-removal or conversion (for conversion there’s also pandoc). And the viewer can be started as a separate program, or other document viewers (like Okular on Linux) can be used.
Also, Callibre has lots of ways to customize the UI or disabling functionality via the plugin system. You can probably turn off most things you don’t use.