In an email sent out today, Apple has begun to push OS X developers to submit their Mountain Lion ready applications to the Mac App Store. This email follows the release today of the OS X Mountain Lion GM build to developers.
According to Apple:
Make sure your apps take advantage of the great new features in OS X Mountain Lion when the world’s most advanced operating system ships to millions of customers worldwide. Download OS X Mountain Lion GM seed and Xcode 4.4 GM seed, now available on the Mac Dev Center. Build your apps with these latest seeds, then test and submit for review. You can also submit iOS apps that take advantage of the new cross-platform Game Center Groups, so they’ll be available when OS X Mountain Lion ships.
Apple wants to make sure that developers have their Mountain Lion applications submitted as soon as possible, since Mountain Lion is due to ship to customers sometime in July for $19.99