I view this more like Heroku and how they have git servers. Sure, Heroku has git servers but isn't trying to be GitHub (a web interface over git and development communication in general). This appears to just be a convenience for deploying your code.
Also, given Amazon's awful reputation for building UIs that people actually want to use, I doubt they could build something to compete with GitHub anyway.
Because this'll integrate heavily with Amazon's other offerings in time. I'd expect click-to-deploy for Node apps to wind up in the interface fairly quickly.
> I'm a little confused. Why would I use this instead of Github?
I haven't actually done the math yet, but it looks like it may be more economical for large numbers of private repos. For Open Source projects, there's probably no reason to use this, but for companies and other organizations who want Git hosting for private code, it might make sense. And the IAM integration actually could be useful if you're already a heavy user of Amazon AWS services.
Also, given Amazon's awful reputation for building UIs that people actually want to use, I doubt they could build something to compete with GitHub anyway.