Sony released the Xperia S open source archive today, providing all the tools necessary to build a kernel and start cooking up ROMs for the Xperia S from Sony's source code. In a post to Sony Mobile's developer blog today, the company also noted that the opening of the Xperia S archive marks the first time Sony has published source code for a product built around Qualcomm's Snapdragon S3.
The post goes on to advise that in order to flash the software, users will need to complete a few extra steps and run a special script (which is linked, along with a proprietary firmware file, in the original post). Going the extra mile, Sony also provided building instructions, as well as an open invitation to pose any questions that may arise in the process. Those eager to start cooking for the Xperia S should check out the device's open source archive, and visit Sony's original post linked below.
Source: Sony Mobile developer blog