[Zope] Final application distribution policies

How do you do when you finish an application that will run on your clients' server, and you don't want them to modify the source code, due your need to reduce future failure risks, not imputable to you or your code? I know that with respect to Zope's license, binary distribuitons are allowed, so how would you protect/close a finished application? What would your primary concerns be and what security policies would you use? Thanks in advance, Ausum