IIRC, the specific section that most people are refering to is:
You may not use technical measures to obstruct or control the reading
or further copying of the copies you make or distribute.
This means that you cannot publish them under DRM systems to restrict
the possessors of the copies. It isn't supposed to refer to use of
encryption or file access control on your own copy.
I will talk with our lawyer and see if that sentence needs to be
clarified.