Valve's release of the Steam Links SDK has support for the OpenGL ES 2.0, Qt 5.4, and SDL 2.0 APIs. Apps can be loaded onto the Steam Link via copying them to a USB drive in a steamlink/apps folder and then power cycling the hardware. Valve also revealed there is SSH support for the Steam Link if wishing to debug any apps on the device.
As part of the Steam Link SDK debut, they also revealed that this device is using a single-core ARMv7 processor running at 1GHz, has about 256MB of available RAM, and 500MB of usable flash storage. The firmware is using the Linux 3.8 kernel and glibc 2.19.
More details on the Steam Link SDK via the new GitHub repository. If this makes you now interested in the Steam Link, you can find it for $50 USD on Amazon.