Jelly Bean was announced at Google I/O just recently, but a posting from Google's Android open source guru, Jean-Baptiste Queru has confirmed that Android 4.1 is hitting the Android Open Source Project (AOSP) repository right now. Time for the developers among you to update your clients to get all the official bits.
This release will be tagged as android-4.1.1_r1 in AOSP. While the source is going live now, the full proprietary binaries for Google-blessed devices won't be rolled out until later. Google plans to directly support the Nexus 7, Galaxy Nexus, Nexus S, and Xoom through AOSP. Be aware that the addition of the Jelly Bean code to AOSP doesn't mean any OTA updates are on the way.