Actually that's an interesting point. Patents must be obtained in every country where you want to enforce them. So if you have a product that will never be sold

Actually that's an interesting point. Patents must be obtained in every country where you want to enforce them. So if you have a product that will never be sold or used in a country where React is patented, you might be ok. However, the license may still apply and you would need to determine whether you are agreeing to respect the patent regardless of it's validity in your country. So many of these questions would be easier to answer if anyone knew the patents FB actually has obtained on this technology.