On the first pass, it's a not particularly interesting reversal of "Nothing is true, everything is permitted", which was attributed to the original assassins.

In context, it seems to be a joke from a site that offers a patient-centered view of psychiatric and some other drugs-- there's a serious effort at accuracy (as far as I can tell from a casual look), but patients have limited choices because of restrictions on prescription drugs. A that point, I'd say it's a reasonably clever joke, but not a maxim which applies to life in general.