[unknownian]

That's not just what it says. If it just said that, that would be fine.

It says making "any claim" against a Facebook patent will terminate your right to use the software. Facebook gets to protect its own software patents: "that any right in any patent claim of Facebook is invalid or unenforceable."

The other lines are okay, it seems.

I am not an IP law expert or lawyer though, but the writing seems pretty simple.

[EdwardMSmith]

I'm not a lawyer either, but isn't the word "claim" a term of art in law. Doesn't it have a specific meaning distinct from the common usage?

[teraflop]

"Claim" has a specific meaning in the sense of the invention "claimed" by a patent. But Facebook's patent grant is clearly not using it in that context: "any claim (including by filing any lawsuit, assertion or other action)".