Is all my CMS content created with Dragdropr hosted by DragDropr?

Yes, it is, but only additionally to Magento CMS.

When you use our awesome DragDropr builder, we create a beautiful and plain HTML code and add it directly to the typical TinyMCE rich text editor used by Magento by default. So all the code is there and it's absolutely yours. 

However, we also store a backup of the pages you created within our backend and you can easily duplicate pages, create templates or backup to your store if needed.