Android has been ported to UDOO QUAD/DUAL.
The stable Android version for UDOO QUAD/DUAL is based on Android Marshmallow 6.0.1. The previous release, still available for download, is KitKat 4.4.2.
SD card images can be downloaded from the image section of the website.
Instructions to download and flash the SD card image are available on this page.
Instructions to download and compile the Android Source code for UDOO QUAD/DUAL are available on the Compile Android From Source section.