The development environment for the IRIS HubOS is currently based on the Yocto 2.7.4 "Warrior" release. The proprietary hardware is similar to that of the BeagleBone Black for our second generation Hub, and a custom NXP imx6DualLite design for the 3rd generation Hub.
The changes to the OSS packages used are marked with "IRIS Change" additions to the files touched. A list of changes can be found in the ChangeLog_oss.txt file.