To be 100% clear: we do not prevent anyone from using Memex to build a Memex competitor. That clause was boilerplate our lawyers included, and it doesn't reflect how we operate or what we intend to enforce. I should have caught it and we'll fix it.
On the Usage Data side, your code is never stored anywhere other than your machine when you use Memex. And you can enable "Privacy mode" to not have your prompts stored either.