Apple has today seeded the third beta of iOS 9.3.3. This comes two weeks after seeding the second beta. What’s new with this version is unknown, but likely features some bug fixes and improvements. Apple doesn’t usually seed versions this small, which hints that they made some changes that might effect developers’ apps.
To get this version, developers can go to Settings > General > Software update > iOS 9.3.3 Beta 3. If you don’t have it yet, you can download it from the Apple Developer Center at developer.apple.com/downloads.