The Department of justice needs witnesses because they’re trying to prove that ez lynk is profiting from the distribution of “emission disabling software” They are not going after any of these individual users. Tldr: they’re trying to get the mod taken off the market.

That's the narrative. In reality, you don't need a list of every user to find a handful of witnesses. This is very clearly a power play - the feds can't make their case so they're making distributing the app a major PR headache for the platforms distributing the app. Apple and google will quietly change their user agreements to not permit these sorts of apps on their stores. The company's leadership will likely escape prosecution but their business will be crippled if not destroyed despite not being proved guilty of violating any law.