Unfortunately the GPU is a Mali, so software-wise it's not completely open, but the hardware is fully open-source and the SoC datasheets are available.
- ARM licenses its designs so that would make their SoC design not open-source (both CPU and GPU)? (a sub question: they didn't specify in the main page who made the Mali. ARM doesn't make chips itself).
- By "software-wise" you mean the GPU driver? the way nVidia and AMD drivers are not open-source. But since people are trying to reverse-engineer those GPUs to make open-source drivers (nouveau and xf86-video-ati respectively), do you think this could be done for Mali too?
Unfortunately the GPU is a Mali, so software-wise it's not completely open, but the hardware is fully open-source and the SoC datasheets are available.