In a statement posted to an Android developer mailing list, Google software engineer Jean-Baptiste Queru announced that the Android 4.0 source code is being rolled out to the public Android Open Source Project version control repository where it will be available for the public to download.

Android 4.0, codenamed Ice Cream Sandwich (ICS), is the latest version of Google’s mobile operating system. It will ship on the upcoming Galaxy Nexus handset, which was unveiled last month at an event in Hong Kong. ICS is a significant update because it brings together Android’s tablet and phone interfaces in a unified environment.

The availability of ICS source code is especially significant because it marks the first time that Google’s tablet code has been opened to public scrutiny. Google previously withheld the source code of Honeycomb, the company’s tablet-centric version of the operating system, and only provided access to select partners. That disappointing move prevented the independent Android community from building custom ROMs for devices like the Motorola Xoom.

Google contended that corners were cut during Honeycomb development and that the software was held back because it was unsuitable for widespread availability. The decision to unilaterally withhold access to source code for competitive reasons undermined the company’s early claims about the extent of Android’s openness.

The Honeycomb source code is technically included in today’s ICS code drop, because ICS was developed on top of the Honeycomb code tree. Google has not actually tagged the specific Honeycomb releases, however, in order to discourage third-party developers from creating Honeycomb builds of Android.

“This release includes the full history of the Android source code tree, which naturally includes all the source code for the Honeycomb releases. However, since Honeycomb was a little incomplete, we want everyone to focus on Ice Cream Sandwich,” wrote Queru. “So, we haven’t created any tags that correspond to the Honeycomb releases (even though the changes are present in the history.)”

The source code release today will significantly ease tensions between Google and the third-party Android platform development community. The fact that the company is publishing the code before the availability of the first Android 4.0 device is a commendable improvement over Google’s previous Android code release practices.

Android 4.0 code is now available, but the code drop doesn’t fully ameliorate the fundamental issue raised by Honeycomb: Google has the ability to withhold code for any given release as it sees fit, because the actual Android development process occurs behind closed doors. Publishing the ICS source is a welcome move, but changes in governance are still needed to make Android a truly open project.