My take on all this is Facebook's legal team seems to be sending a message to the open source community that they should come for the ideas, but wait for a truly open source alternative to come out before using those ideas in their own products.
But if you are using ideas from their software, you are infringing patents too.
Well duh thats the idea. Then they can sue you. More work for FB's legal team too.
I'm obviously not condoning patent infringement. The idea is to learn from useful ideas and implement a non-infringing equivalent as an open source project. You can't patent "math", or "computer science", or ideas comparably broad.
you shouldn't be able to patent a query language for a graph either but here we are