"The Source Files and Assets, in combination with the use of any required tools, should be able to successfully build a complete working version of the game. Such tools must be available to the public (freely or commercially) prior to the start of the contest."

So, the devs don't actually submit a working, double-clickable version of our game - we only submit the files needed to make the build and we leave the creation of the build to the people running the contest? Is that right?

Absolutely not. You submit your game in two forms: one for public, double-clickable consumption, and one for the source code.

If an entry was made in Unity, your conception of this rule would make no sense, since licenses cost gazillions of dollars and the contest runner people would have to buy one. Also, I really doubt that Carlos has the time or inclination to build every single entry himself.

Thanks. That makes more sense to me. I just didn't see anything about that in the general rules and submission info.