Given that the people behind Pandora actually want the 3D to be used I really don't think the OpenGL drivers/libraries will cost money. They'll probably be binary only modules. I wouldn't expect the low level details of the PowerVR chip to be available, but it's possible.
It certainly will cost you nothing to use the OpenGL ES drivers – apart from buying the device itself, of course. Low level details of the GPU will not be open, though.