Microsoft is stepping things up in its plan to rid itself of the Metro branding, as the company's app naming guide for developers has been updated with a clause that bans the term from app titles. Beneath a section called "Don't use names trademarked by others" is a note that reads: "Make sure your app name doesn't include the word metro. Apps with a name that includes the word metro will fail certification and won't be listed in the Windows Store."
That's a fairly hard-line approach: it's believed that Microsoft dropped its Metro codename in order to avoid a trademark dispute with a German partner (and it has previously advised developers to move away from the branding), but refusing to certify any app with "metro" in its name means that it's forcing third-party developers to avoid a trademark dispute, too. It also raises a bigger issue: not only will well-known apps like MetroTwit be hurt by this policy, but also apps that aren't leveraging Microsoft's branding will likely get caught in the crossfire (e.g. a transit app for Paris' Metro). The replacement for "Metro," in case you missed it, is the far less appealing "Modern UI Style."
Update: The wording has just been mysteriously removed from the guide. We've reached out to Microsoft to get more information on what the policy is, and we'll update this post again when we hear back.