How do I stop GitHub Conduit? How do I stop GitHub Conduit and keep GitHub.app from reinstalling the job in launchd?
There are two steps to stopping GitHub Conduit: telling GitHub.app to not re-install the job with launchd and telling launchd to not run it anymore.

Disable Conduit installation:

defaults write com.github.GitHub GHShouldDisableConduit -bool yes

Remove launchd job:

launchctl remove com.github.GitHub.Conduit