SpaceChem Question

Read the FAQ again, bro.

This. Feel free to report the giveaway if it broke the rules like this one:

When you submit a Humble Bundle, it is only acceptable to have an unactivated gift URL to provide to the winner. Members giving away Steam keys and the like will be warned, have their giveaways removed, and if they continue, may result in a suspension.

You can keep the game though.

It is against the rules to give away individual keys from Humble Bundles regardless of whether they're still on sale or not, so you could report it and the individual will be reprimanded (or have their account suspended if it has been a habitual thing). But beyond that there is nothing really to do. You won't lose the game either way.