Zombies, Run! developer Six to Start has revealed that it’s complicated, but not impossible to set up a pre-order system for an iOS game. The London-based studio was able to work directly with Apple to ensure backers for its successful Kickstarter campaign would be able to receive the 3000 plus copies of the game they had been promised in return for their donations.

Typically, the iTunes App Store allots 50 promotional codes per version of a game — enough for reviews, but not enough for a crowd-sourcing campaign, where the most common reward for donating is a free copy of the finished product.

Six to Start’s campaign ended on Oct. 2011 with over $72,000 raised and more than 3,400 backers, almost all of whom had essentially pre-ordered a copy of the game. After discussing plans with Apple, the company created two copies of the game, the standard, $7.99 paid version of Zombies Run, and a free version called ZR Advance. Six to Start declined to explain in more detail how exactly Apple contacted them or who they talked to at the company.

Backers were asked to set up a password connected to their email account in advance, and on the day of release, Kickstarter contributors were able to use their email and password to unlock the full game’s content from within the free app.

While not an official strategy endorsed by Apple, its an efficient solution for an independent developer with a relatively small amount of product to distribute. It’s unclear, however, what sort of deal the developers behind bigger crowd-sourcing campaigns with iOS rewards (the successful République Kickstarter has promised over 7,000 copies of the game) will be able to strike with Apple, and if Apple will still allow such a workaround in the future if crowd-sourcing becomes more common.

Developers considering crowd-sourcing the funding for mobile games through platforms like Kickstarter, Indiegogo or AppStori, should carefully consider iOS distribution before launching their campaigns.