http://aomedia.org/press-releases/
AOMedia seemed to do that quite quickly when Facebook joined. Maybe Apple asked them not to, but I don't see why Apple would.
> Founding members are Amazon, Apple, ARM, Cisco, Facebook, Google, IBM, Intel, Microsoft, Mozilla, Netflix and NVIDIA.
A similar sentence exists on AOM's about page[2].
The Thor codec tech they contributed is all about focusing on that use case, real-time encoding etc.
They also previously contributed the h.264 plugin to Mozilla (they already pay the capped royalty amount so it's effectively free for them) to ensure their hardware components would be able to interoperate with popular browsers using WebRTC.