Since I specifically mentioned the likelihood that simply installing an otherwise compatible and licensed application would fall under fair use, no, I haven't forgot about that or suggested that installing an application such as BiteSMS results in piracy. Of course, if the OS is modified in any way to provide additional functionality to the applications, you are solidly in a gray area.
Since iOS doesn't provide any mechanism to replace the built in SMS app as the default messaging app, I wouldn't be comfortable with the legality without understanding exactly what changes are made.
Your entire rational and argument regarding Jailbreaking and its legality is mind boggling. As said above, is every news source wrong?
What are they teaching you guys up in Chapel Hill?