Lots of people seem to be getting tied up arguing that money doesn't make something non-free. I think we can all agree on that and move on: Move on to discussing the impact of the involvement of more paid developers.
If you want to ensure the health of a project, you need to be aware of forces at work within it.
There are paid developers who act like kernel-hackers and then there are paid developers who simply try to fix bug X in release Y for hardware Z which is being released next Tuesday. This isn't evil, but neither is it true to say it's irrelevant.
Finally we should acknowledge that the financial self-interest of companies rarely aligns perfectly with the principals of freedom: That's OK different developers ideas rarely align completely, but it is a different sort of force, and growth of it does influence the nature of the community and the development process.