Everything in openshift is open source at https://github.com/openshift/origin. The commercial version is long term support, security response and errata, and the stability around that. There's nothing that is withheld from the open source project. It is not open core.
Edit: I forgot, the logo is not open source. So the logo is withheld :)
It's a pretty common model amongst these companies, and hey they've got to make money somehow :)