"It is the fact that Okular actively resists its users' obvious intent
which I find objectionable."
What on earth are you talking about? Okular provides a toggle for the
user to express their intent, i.e. honor or ignore the copy restriction
flag, and honors the setting chosen by the user.
I hit this "problem" during my first day of using KDE4, which uses Okular.
I was confused for the approximately 5 seconds it took to read and
comprehend the greyed-out message, and then another 10 seconds to find and
toggle the setting. That's utterly trivial compared to, say, figuring out
how to make Gnome honor my intent as a user to respond to single
right-mouse clicks rather than double left-mouse clicks :-)