It took a little while but I'm thinking the main point here is that you store your content in the Osmek system.

Then the content can be published to multiple sources such as an iOS app, website, tablet app, mobile website.

I just don't understand how this is different from having your own database with the content. What's the difference between this and say Django's auto generated admin interface (setup with proper permissions) ?

Why can't my apps just pull stuff out of the database or through my own API ?

I'm sure I'm missing something because this seems expensive so it must be worth a lot to somebody. But why ?