Mali Open Source? No not the complete driver stack. However they have released both commercially available license drivers and substitute Open Source drivers for use that fully functional for most any Linux or Android version OS requiring a GPL license:
http://malideveloper.arm.com/develop-for-mali/drivers/open-source-mali-gpus-linux-kernel-device-drivers/

http://en.wikipedia.org/wiki/Mali_(GPU)

The Lima Driver is a reverse engineered Open Source Mali Driver, minus the proprietary DRM component. So having PowerVR Open Source Drivers still isn’t a chip advantage for Imagination. Since they don’t have a full stack Open Source driver either…. yet. They are like most other proprietary drivers merely shimmed into the Linux kernel or driver module :
http://powervr.gnu.org.ve/doku.php

So get your facts straight before making an irrelevant post yourself!

Lots of cubieboards use Mali GPU. I don’t always don’t know answers before asking.