Re: Two and a half years ago I wrote
Imagination had offered themselves up for sale to Apple back then but they weren't interested, at least not at whatever price was being asked.
I figure either Imagination's new deep pocketed owners were going to sue (there were rumors that was going to happen soon) over patents so they are licensing just patents, or the new generation GPU design Imagination announced recently performs better than Apple's internally designed GPU so they are licensing the design. We'll probably never know for sure, unless the Metal APIs for future Apple SoCs include something that makes licensing the new generation of Imagination cores obvious.
While GPU design is a patent minefield, everyone else designing GPUs also does some CPU designs as well and Apple has a huge patent warchest there. So AMD, Nvidia, Intel or ARM couldn't sue Apple over GPU patents because Apple would be able to countersue over CPU patents and a cross licensing deal would result, like they always do when two companies with big bunches of patents the other uses go after one another.
I think Apple may already have a cross licensing deal with Intel, though I'm not sure - they license each other's "IP" but who knows how broad that agreement really is. And of course they have an architectural license from ARM, which would obviously include a patent cross license deal at least for CPUs. Not sure whether it would include GPUs, but ARM isn't likely to go suing one of their biggest customers anyway.
Imagination is really the only major GPU player that doesn't also do CPUs, and thus the only one who could hold Apple's feet to the fire with a patent lawsuit.