Linaro is an engineering non-profit, support by many of the major players, to improve support for the ARM ecosystem. This includes improvements to GCC, LLVM, the Linux kernel, various libc's, AOSP, ... They also provide Ubuntu, Debian and Android RFS images for supported reference boards.
I understand that they went with a Mali GPU, since it is the reference GPU design from ARM. However, it is unfortunate that there is no open source driver for this platform. Maybe this will change in the future.