Recruiting your users' systems into a botnet is not an acceptable way to make an app "economically viable" any more than, say, installing a rootkit on their systems.

the fsf has never really been concerned with commercial viability. They're the worst audience for this sort of argument.

and I doubt these apps are really Free versions - do they support user modifications and access to the code? If they did support the four freedoms maybe the fsf would have something positive to say to balance it out?