The retropie setup script is not used for a reason in the new version.
If you use it, at least on a rpi2, it will install all kind of stuff and most of that cannot be found in the debian jessie repos, so my first script was a try to solve that with using the raspbian repo. It was not safe hiwever and could destroy your installation.
It might still work fine on a rpi 1. There you can use my first script to get everything setup but be aware that it could mess up your system as osmc on rpi1 is based on raspbian but still ships many custom pavkages you could overwrite with it rendering your system unuseable.