The code for the latest version of Android — 4.0, also known as Ice Cream Sandwich — is now in the wild.

According to a post from Jean-Baptiste M. “JBQ” Queru, a software engineer on the Android Open Source Project, the code is still in the process of being uploaded, and developers are advised to wait til it’s fully complete before they start downloading it themselves. But it’ll be available very soon.

This is a huge deal for a few reasons.

For one, Android 4.0 includes some major improvements over both Gingerbread and Honeycomb, which are the versions of Android that are shipping on current Android devices. These include new API calls, performance improvements, and more.

But more important: it’s the first time Google has open-sourced a version of Android that’s optimized for tablets as well as phones. Now, obviously devices running Android 3.x Honeycomb have been around since early this year. But Google opted not to release the source code for Honeycomb. The reason? It had been thrown together quickly, and Google had to take some shortcuts to get it out the door (they were also concerned that third parties would try to port Honeycomb back to phones, which it isn’t suited for).

The open sourcing of ICS will allow manufacturers who aren’t working directly with Google to pump out tablets of their own (there are some low-cost tablet devices out there shipping with Gingerbread, simply because they couldn’t use Honeycomb). And it also means that custom ROM developers like CyanogenMod can tweak the code, port it to older devices, and more.

A couple of other interesting notes: the version of ICS that’s being open sourced is 4.0.1, and developers can download an image of the Galaxy Nexus, which has the build target full_maguro.

Oh, and if you really want to look at the Honeycomb source, it’s in there too (since it is an ancestor to Ice Cream Sandwich). But Google is discouraging anyone from actually using it.