I'm a bit sick about those people afraid of "spooky forks", if something got forked either branches could live on their forces or one dies.
Indeed but if it wasn't a problem for anyone, and nobody ever cared or anticipated it, projects like Blender wouldn't be cared for by the Blender Foundation for example. They're explicitly set up to manage the Blender source code and make sure development sticks to one track. There is one version of Blender at the end of the day because of this.
Blender is opensource and hasn't forked. So, opensourcing a project doesn't mean it will
fork. Anyone who wants to can fork blender, yet nobody has done so. The Blender Foundation has no power to prevent forking and wasn't created to prevent forks. It was created to help further development. Such a foundation (or any of a number of other organisation forms) may work just as well for other projects, including projects for graphic card drivers.
And there's nothing to prevent a company from opensourcing drivers and yet managing their own source tree to create drivers that are under their control in order to be able to maintain the conditions necessary to be able to certify those drivers for hardware and/or OS'es.
Even though opensource means anyone may fork and may alter the code and produce patches does not mean that any such modifications must be accepted in every development tree. So imho forking is not something a company should worry about. And making source code available under an open source license does not mean giving away copyright. And it's always possible to license the code under multiple licenses too. IP is another issue, but that's a different discussion altogether :)