Re: @AC Here's the reality... its a scam in favor of Facebook.
"If I revoke your rights to use the patented code, then I have the right to sue you for patent infringement."
Well, no, you don't. You might do in certain interpretations, you almost certainly don't. That's why this is hypothetical. There is a concept called an "implied license".
Let's talk about physical things for a second. Let's say I'm Ford. I'm not, but I could be. I loan you a car. I hold many patents on the operation of that car. I make no mention of the patents but we sign an agreement letting you use the car.
Patent agreements never come into it. The use of the patents is implied by the use of the product. What is not implied is a license to modify and reuse. Patent infringement doesn't happen through use, it happens through production, sale and "imitation".
Now of course software isn't physical and that's one of the many reasons why software patents are bullshit. But the core concept is the same. Your BSD rights do not go away. You still have, under copyright law, the right to do pretty much whatever you want with the software.
What Facebook are saying is that they reserve the right to sue you for patent violations (as distinct from copyright) if you ever come into conflict with them. Whether or not they actually have the right to sue you and whether or not they would be successful is moot. They're a $500bn or whatever company threatening you with a big fucking stick. Abusing FOSS to do that is not OK, which is why the ASF has banned the approach for its project.
Predictions of doom are hyperbole driven by poor misreading of other people's poor analysis.