I can’t see how this is true as there are tons of companies selling access to data obtained from the Twitter API such as social media monitoring companies (Sprinklr, Meltwater)
If you are creating a Twitter app, and letting users login via Twitter and then using those user tokens to make API calls, that’s a good first step, I am not sure if you are doing this already.
Other than that, I would just make sure you position your service as something that benefits Twitter, describe it as something that allows you to create better tweets or engage with your followers better. The internet is filled with apps that sell Twitter data like Mention.com, SocialRank, and Social Animal.
So either way sounds like a ToS violation. Which Twitter is usually pretty aggressive about shutting down.