I'm the guy who did the arm mali gpu reverse engineering and who started the whole open source drivers for arm movement (and modesetting, and the free ati driver, and ...). From the start, i planned for IMG to be singled out, and provided the reasons for doing so. If you hear or heard anyone state, in the last decade, that powervr SGX code is horrible and the hw is not worth reverse engineering, they have been repeating my statements and insights into that topic.
According to my insider info, IMG actively thought about going open back in 2014 and 2015, but each time could not get itself to spend the resources. There were also quite some rumours flying around. Last summer, as a corona babysitting project, i plugged my M3D in a pci-e-to-pci adapter, hacked QEMU to handle the iommu properly, and have been running Win98SE over X to my laptop. Capture was incomplete though, and replay was not happening. I spent a lot of time (on and off) with ghidra and found what i had been missing back in january. Then real life interrupted again, and this lay dormant.
So then my original plan worked out. With a 5-8y delay, but it worked out. But it killed what would have been the perfect troll, the start of an actual open source driver for powervr, but not a "useful" powervr... And i spent a few weeks debating whether i should continue working on getting a first triangle out, and doing a but of further code and a release still... And then IMG went above and beyond. It costs them barely anything, and they are getting a lot of goodwill out of this.
I have the previously publicly available demos ported to build under mingw32. Once i revive my build machine, i will get that code out on github.
As for mesa... This is very early and weird fixed function hw, i do not think this has a place in modern mesa. Parts of mesa could be retooled to provide the gl translation layer though.