Oh yes, from looking at them essentially forking it, it looks like they didn't work together.

But my question was whether or not they _did_ work together, one of the tech sites wrote that they did. I will try and find the reference.

I seem to remember that as well but I have no reference for it.

They actually forked earlier than that. Everything I've read has said the forked 2.1, which means Amazon has been developing the Fire for some time now, with impressive secrecy to boot.