https://github.com/kohsuke/github-api/blob/master/src/main/java/org/kohsuke/github/GHRepository.java#L96

GHRepository doesn't take into account whether or not the client is speaking with the public github.com or if it's talking to a github enterprise instance. Consequently, when you call getGitTransportUrl() or gitHttpTransportUrl() it only ever returns a github.com URL, which won't work for github enterprise hosted repositories.