You can't transfer DRM protected ebooks to read on other devices. (the-ebook-reader.com)
With the release of Content Server 4.1, publishers and content distributors now have the additional option to protect eBooks using «password - only» authorization. (matt-phillips.com)
Since DRM protects eBooks from unauthorized copying and distribution, it has mostly become a requirement for selling eBooks. (editionguard.com)