Apple has released an update to OS X Mountain Lion Developer Preview 4, made available through the Mac App Store, to developers using the build that was released during WWDC 2012. If you're running Mountain Lion DP4, just launch the Mac App Store and check your Updates tab to find the software. It's a little over 1 GB in size, and will require a reboot to install.
Alongisde the iOS 6 beta, Apple has also seeded OS X Mountain Lion Developer Preview 4, making it available in its Dev Center. This is a near-final version of Mountain Lion, and as such, there aren't many areas of concern listed in the seed note. It makes sense, since Mountain Lion will be released next month. If you're a Mac developer, you can grab build 12A239 now, as promised in the WWDC 2012 keynote.