At the end of last month, MIPS announced the $125 Karbonn Mobiles Android Jelly Bean Tablet powered by Ingzenic MIPS-Based JZ4770 SoC. Today, they released Android 4.1.1 source code for MIPS
Before downloading the Android source code, make sure you have a properly setup Linux workstation.
Here are the instructions to checkout MIPS Android 4.1.1:
repo init -u git://github.com/MIPS/manifests.git -b dev-mips-jb -m mips-jb-4.1.1_r1.xml
You can read the release notes for more details about the current status of the MIPS Android Jelly Bean port.
Myriad Dalvik turbo, an alternative Dalvik implement that is much faster than the default Dalvik engine (at least on MIPS), is not yet available for Android 4.1, but should be soon.
All MIPS Android source code can also be viewed online at http://www.github.com/mips.