This essentially boils down to "any content sourced from the api must be displayed unmodified, in its entirety, and be properly attributed." It's a pretty standard thing across the entire internet. really, the only strange thing is the insistence that the author's username must be on a separate line from the tweet.

It's a great way to restrict clients that integrate with other services, especially competitors like Facebook.

How are they expecting to enforce that? Are they really going to download and test every third-party app?

Reviewing the most popular X apps is easy. Apps that no one uses don't matter.

Require screenshot submissions, hire a bunch of temps, and they're all set.

... or use their recently open-sourced mechanical turk library.