[blindpirate]

Hi, I fully understand your concern (because if I were you I might think the same as you). First of all, a GitHub app can only "act on your behalf" in the repository/organization where it's installed (which is only https://github.com/ByteLegendQuest). It has no permission to access any other resources outside.

Yes, it's using Kotlin multiplatform, so I can write code once and use it at both frontend and backend.

Because the game highly depends on GitHub API and GitHub actions (when you submit code answer in the game, you are actually creating pull requests), using a GitHub account would be the best option.