BlackBerry released the developer OS 10.3.1.396 and it is a full OS so you can use it for your device, unlike other developer OS releases. HOWEVER, please remember this is still a developer OS so it will be buggy but if you feel so inclined, you may want to give it a try.
Please note the BlackBerry Blend does not work on this version and there is not an OS release for the newly launched BlackBerry Passport. Also, as always, BlackBerryOS.com is not responsible for any issues or problems that may arise as a result of installing this developer OS. We assume no liability.
That being said, here are links to the active downloads for 10.3.1.396. When more devices become available for this OS, we will add them.
Source: CB Forums