Apple OS X Mavericks Developer Preview 4 has also been released to developers registered in Apple's Mac Developer program. The update comes just two weeks after the release of Developer Preview 3 but doesn't include a list of changes this time.If you are eligible to download the update, it is available through the Mac App Store and is a little over a gigabyte in size. The update brings several stability and performance improvements to OS X 10.9 platform along with several bug fixes.