But should the dead rise from their grave, all bets are off.

The terms and service page of the Lumberyard game engine, which most people are likely to skip over before agreeing to it, is full of things you can’t do. Licensees, for instance, are not allowed to use the engine for life-critical or safety-critical systems, including medical equipment, automated transportation systems, autonomous vehicles, aircraft or air traffic control, nuclear facilities, or manned spacecraft.

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So that’s a big no-no if you want to use a video game engine to fly your garage rocket to Mars. (Sorry, Elon Musk!) However, should we be overrun with zombies, Amazon was kind enough to supply a loophole in section 57.10.

“This restriction will not apply in the event of the occurrence (certified by the United States Centers for Disease Control or successor body) of a widespread viral infection transmitted via bites or contact with bodily fluids that causes human corpses to reanimate and seek to consume living human flesh, blood, brain or nerve tissue and is likely to result in the fall of organized civilization,” the company says.

Amazon will not charge game makers any sort of royalty or subscription fee for using Lumberyard to create games for PC, Xbox One, and PlayStation 4. Instead, the company plans to monetize the engine through the required use of its Amazon Web Services (AWS) cloud computing arm. (Technically, if you have your own cloud server set up in your home or office, you can use that — but that’s pretty uncommon.)

For more on zombies, watch:

Developers who use Lumberyard will pay a fee for each daily active user (DAU), as well as any normal costs for using Amazon’s cloud computing service. (That’s why you’re not allowed to use other services.)

Want out of that deal? You’d better start spending more time with Rick Grimes.