From the page you linked.

Digital rights management (DRM) is a generic term for access control technologies that can be used by hardware manufacturers, publishers, copyright holders and individuals to impose limitations on the usage of digital content and devices. The term is used to describe any technology that inhibits uses of digital content not desired or intended by the content provider. The term does not generally refer to other forms of copy protection which can be circumvented without modifying the file or device, such as serial numbers or keyfiles.

That is exactly what the post talks about. They say that they are aware that applications can be copied/installed without authorization (euphemism for pirated) either via apt-get or by dpkg -i is not enough for them (so they are missing what ? Hint: some form of DRM). Do we really still want to beat this dead terminology horse ?

EDIT: extended quote from wikipedia