Best practice for commercial WordPress themes and version control

I’ve long kept my WordPress sites in version control (and if you’re not doing the same, let Mark Jaquith tell you why you should), and I typically pull in themes and plugins as git submodules. I recently purchased the Genesis Theme to use on a website I’m building for my church, and I’m trying to figure out how best to put it in version control.

Because Genesis is a paid theme, I don’t really want to put it in a public GitHub repository, and thereby allow anyone to use it without paying. Though to be clear, it’s licensed under the GPL so I would have every right to post it publicly, I just don’t really want to. But it also seems wasteful to use one of my few private repos on GitHub just for this. It’d be really great if StudioPress had a git repo that paying customers had read access to that they could use for exactly this purpose. They have a GitHub account, so maybe there’s a private repo behind there and I just can’t see it?

I’m curious how others are handling this for Genesis, or any other paid WordPress plugin or theme that is also open source.