Google has refused to release the source code of Android 3.x , aka Honeycomb.
Android been opensource, this is expected.
Google gives a very B*tchy excuse in the form that if they release the course, open source developers will port the OS to phones. The OS was done specifically for tablets and made some compromises which will give users a bad user experience on phones, and Google cares so much it doesn't want to cause this.
At the end, its Google's software though, if open source devs really want, they should work their asses off and add same functionality to 2.x