gh-mirror is a simple way to mirror an org's GitHub repositories locally, maintaining the upstream repository metadata, and keep them updated easily. See the blog post I wrote it for to get more information about how to use it in a useful way. For private repositories, ensure that the user running gh-mirror has a sufficient .netrc file for github api and repository access.
$ gh-mirror exampleorg
Cloning into bare repository 'foo.git'...
remote: Counting objects: 7, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 7 (delta 0), reused 6 (delta 0)
Receiving objects: 100% (7/7), done.
Checking connectivity... done.
Cloning into bare repository 'bar.git'...
[...]
gh-mirror is ISC licensed. See the LICENSE file for full details.