This is a basic marketing strategy for a service like this. I've seen at least three projects in the last few months that require API access say the same thing, but can't completely convince me that they can secure the API data. I'd advise people to be cautious if a centralized service requires your API key, especially if an open-source trading tool becomes freely available.

Btw, OP just woke up from a long period of inactivity, his last post was in 2018, and then he made a promotional post with a referral link like this. Anyone should be aware about that issue before they try the service. Better to be safe than sorry.