The GitHub plugin fails to add a webhook on a repository owned by someone else whereas it has rights to do so.
The repository is owned by our enterprise (GitHub "organization"). The configured jenkins user is member of the "owners". So it has rights to edit hooks but the plugin fails when checking the owner.

Jul 20, 2011 2:54:36 PM com.cloudbees.jenkins.GitHubPushTrigger$1 run
WARNING: Failed to add GitHub webhook for GitHubRepository[username=nuxeo,repository=nuxeo-distribution-izpack]
org.kohsuke.github.GHException: Failed to update post-commit hooks
at org.kohsuke.github.GHRepository$1.add(GHRepository.java:229)
at org.kohsuke.github.GHRepository$1.add(GHRepository.java:179)
at com.cloudbees.jenkins.GitHubPushTrigger$1.run(GitHubPushTrigger.java:128)
at hudson.util.SequentialExecutionQueue$QueueEntry.run(SequentialExecutionQueue.java:118)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.io.IOException: Operation not applicable to a repository owned by someone else: nuxeo
at org.kohsuke.github.GHRepository.verifyMine(GHRepository.java:165)
at org.kohsuke.github.GHRepository.access$000(GHRepository.java:49)
at org.kohsuke.github.GHRepository$1.add(GHRepository.java:213)
... 9 more

PS: the github component is missing in Jira.