This one has a variety of balance tweaks, the most substantial of which is to prevent certain kinds of exploits with super-terminals. Warbird and Beam starships also got a heck of a lot more awesome, and mapgen is no longer quite so unkind with where it is able to put Dyson Sphere planets.
This is a standard update that you can download through the
in-game updater itself, if you already have 4.000 or later. When you
launch the game, you'll see the notice of the update having been found
if you're connected to the Internet at the time. If you don't have 4.000 or later, you can download that here.