Earlier quoted context omitted.
It looks like you can commit code to the game by pointing it at a GitHub repository or other methods[1]. I couldn't find documentation on the GitHub integration but here's some people talking about it[2]. [1] http://support.screeps.com/hc/en-us/articles/203022512-Commi... [2] http://support.screeps.com/hc/communities/public/questions/2...
Ahh. Makes sense then - I wonder if GitHub allows granular permissions from OAuth requests? Looks like they don't, unfortunately - https://developer.github.com/v3/oauth/#scopes
public_repo - Grants read/write access to code, commit statuses, collaborators, and deployment statuses for public repositories and organizations. Also required for starring public repositories.
repo - Grants read/write access to code, commit statuses, collaborators, and deployment statuses for public and private repositories and organizations.
Also, I don't think they need write access at all to your repositories, so I think the default no scope would be sufficient
(no scope) - Grants read-only access to public information (includes public user profile info, public repository info, and gists)