Github has private accounts, it's used by thousands of companies developing commercial software. I think it's under $10 a month which gives you several private repo's.
One thing to remember is that github != git. Github has a workflow and a lot of tools to make your life easier, and there are a ton of third party services that hook into github. As far as platforms as a service for source control, no one really touches github, and you have to factor that in to your larger decision on which source control software to use.
Beyond that I would just say stick with a distributed source control system like Mercurial or Git. If you want to be able to manage different branches and merge code without pulling your hair out, don't touch Subversion.