I found this odd too, so I was skeptical of the claim, but I found this sentence on the home page[1] that mentions Apple as a founding member:

> 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].

[1]: http://aomedia.org/ [2]: http://aomedia.org/about-us/