Oracle is notorious for auditing compliance with their database licenses, and shaking down their users for extra money in the event the auditors find something even slightly questionable. There are external consultants that make a pretty good living just preparing companies to withstand those audits.

They haven't been doing that with JDK licenses, so far -- as long as Java had licenses which didn't allow for this kind of gamesmanship. But now that the license has changed, it's a completely legitimate thing to get worried about.