It seems like it would be easier to just create another github user, add it to your organization as a read-only user, and then add each machine's ssh key to tha

It seems like it would be easier to just create another github user, add it to your organization as a read-only user, and then add each machine's ssh key to that user as a real ssh key rather than a deploy key. The downside is that you can't restrict certain machines to certain repositories, but the upside is that it's a lot less complex.