It's another "arcane and idiotic lawyers" situation... Obviously the way the licenses are structured allows distribution of a factory image, but apparently not the subcomponent of that image consisting just of the GPU blobs.
Nonsensical - but the general theme with both this and situation with mako and flo has been "nonsensical lawyer bullshit that makes no sense to any sane person".
For a device to officially be supported by AOSP, I am fairly certain the binaries have to be available as a separate download. Extracting from a device, or even, apparently, a factory image, is not kosher for official AOSP support as far as I can tell.
The end result is you often have cases of devices where the community has no issue supporting a device even though AOSP can't officially do so - the community lives in a legal grey area on MANY of their devices, and the oddball "non-AOSP Nexii" are just another item in this category. (For example, with the CDMA Galaxy Nexus mess, community projects extracted and re-signed the APKs in question, but for many months, those devices were not officially supported by AOSP, because re-signing hacks were a no-no and the licensing forbid redistribution of those items.)
That said, bullshit like this, if it continues, will just burn out the next AOSP lead too, and if upstream keeps getting burned out by lawyer idiocy, community projects that derive from AOSP are going to be in bad shape.