Hey, uh, I just bought this game on the excellent Humble Indie Bundle... but with no key, and just a executable, how can I get free updates when they are released?

I mean, Humble Indie Bundle usually only hosts the downloads until the next bundle is released, and then they're gone.
Normally Humble Indie Bundle games are redeemable on Steam, which I love, but this game isn't and so I have no Steam key.
Since the game didn't ask for a user account or anything, like Minecraft does, how do I get updates?

Is the executable self-updating or something?