This is the GM [Golden Master] build of (Mac) OS X 10.8 Mountain Lion released to developers today. It is likely to be the final build, though that is NOT guaranteed (remember when iOS 5 GM is same as final release? :D) — there have been occasions where Apple has released more than one GM build in the past. With that out of the way, Apple - OS X Mountain Lion - Move your Mac even further ahead enjoy.
OS X Mountain Lion GM Seed 12A269
the dev seed was 4.7GB but this one rings up at 4.05GB?
That likely includes the GUI and stuff for the .app, this is just the DMG pulled out of the .app [installer]