I believe that any modification to the project would stop the App from being valid. The package self validates, and if it's not quite like it was when the package was made, it's not valid.
If you could modify the project to make such changes, you could also sign up for GS (either version), make one package, and give that to all your friends to tweak in order to make their own games for free.
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If you could modify the project to make such changes, you could also sign up for GS (either version), make one package, and give that to all your friends to tweak in order to make their own games for free.