One week after seeding the first beta of OS X Mavericks 10.9.3 Apple has released a second beta build of the update to developers this afternoon.
The last beta added support for a full range of Retina scaling modes for 4K monitors, but release notes for the second beta are light on details of new features – if there are any at all. However, it does ask developers to focus on graphics drivers and audio.
OS X 10.9.3 build 13D17 is available for devs in the Mac Dev Center or via the Mac App Store.