alt Hacker NewsQuite right! They probably wouldn't have wood, but we do!
They might want the wood though, and they might not know how to grow it. From there we can see 2 scenarios. The likelier one hopefully being trade: we could probably teach them to grow wood, and also provide them with seeds, perhaps on exchange for some of their space-faring tech.
Alternatively there's the pessimist scenario, where they're not interested in trading for it, we're not willing to give it freely, and so war ensues.
Personally I'd just give them a few pine-cones and explain basic horticulture as a gesture of good faith, I guess the end result is rather contingent on which human they talk to.
Why would they need our permission to take it? They can grab the seeds from anywhere on the planet, and they can just watch any farmer and/or forest for a couple of years and see how it works.
Of course this is putting aside any ideas of deciphering our books or tapping into the internet. Not much we'd be able to do to species that can travel the stars.