The hack must be built during HackGT and within the 36 hours of hacking.
If you're a new hacker, give this a read first: http://blog.mlh.io/your-first-hackathon-10-07-2013/
After viewing Major League Hacking's official code of conduct (http://static.mlh.io/docs/mlh-code-of-conduct.pdf), we ask you to please adhere to these rules (some content sourced fromhttp://hackathon.launch.co/rules).
1.) Treat all other hackers with utmost respect. Be kind to others. Do not insult or put down other attendees. Behave professionally. Remember that harassment and racist, sexist, or exclusionary jokes are not appropriate for this event. If at any point you see a fellow hacker being harassed, it’s your responsibility to talk to the nearest hackathon organizer.
2.) Treat our sponsors with the utmost respect. Without them, nothing would be possible. Take some time out of your work to go meet and speak with them. If they come over to talk to you, look up from your work and give them a bit of your time. They're here for you! Show them you appreciate it.
3.) Teams can be anywhere from one to four members (unless otherwise specified). All teams retain full ownership of what they have created during the hackathon.
4.) The hackathon is a walled garden. To ensure a level playing field for all contestants, all code, design, art, music, SFX, and assets must be created during the duration of the hackathon. We want to ensure that all participants start off on the same footing and we also want to preserve the true nature of a hackathon. You are, however, free to make plans, create wireframes, and brainstorm prior to the event.
The only exception to this rule would include material that is freely available to the public. Some examples of this would be: public domain images, Creative Commons music, open source libraries, existing APIs and platforms, and the like. Failure to comply may result in the offending team's disqualification.
TL;DR: Bring your blueprints, build at the hackathon. It’s the only way we can compare hacks on a level playing field and fairly award prizes. It’s also what lets you say “I built this at a hackathon."
5.) Have fun. Hackathons are amazing, and so are you. We’re so happy you’re able to hack with us and be a part of our amazing community.
6.) Open your mind. Hacking unites people from across the world from different cultural norms, nationalities, and backgrounds. Be prepared not only to learn something new from your hack, but also from the amazing people around you. Be mindful of the fact that certain content and actions can make the people around you uncomfortable. If your hack contains material that might cross that boundary, talk to a member of the organizing team for a second or third opinion. We'll let you know if you should consider rethinking your hack.
7.) Be the change you want to see in your local community. Never be afraid of competing based on where you come from or have preconceptions of grandeur because you come from a great school. At any time one can achieve greatness. You simply have to see it and seize it.