Ugh gross, As I understand it they grant you a patent exception in a very specific case (Displaying exact schema.org valid tags on a website), but remove any incentive to make tools that consume those schemas, or to extend/enhance the schemas at all.
And they go on to say that there may be strings attached to using things on schema.org, and anyone that doesn't 'sponsor' that particular item on schema.org can withhold their patent completely.
Well that kind of renders this entire thing pointless. They either make this an open patent free standard or they shouldn't even bother with it.
does this mean using the standards on this site may potentially land you in legal trouble later if they decide to enforce these patents?
How is this surprising? If you use their service, you may need a license to a patent of theirs, which is granted to you for use of the service. The patent might not even be issued yet. It seems to me that they are just covering their bases.
So yes, you may need a patent, however, if you are using schema.org, you are not infringing on the patent (because they give you a limited license).
Then again, you might not be infringing on a patent too...