For a starter, we might be able to re-use parts of the sub-theme we've created for www.forensischezorg.nl. I've shared it as a sandbox: https://drupal.org/sandbox/barisw/2063427
This can live as a separate subtheme next to this theme, with a own project page.
Martijn; I believe we discussed the future of this project during the meeting in The Hague with a lot of people. I don't see why you want a new project for the responsive theme. We can easily create a 7.2 branch for the new responsive variant and keep the focus in one place.
I have no intentions to create a project of the Forensische Zorg theme, I just shared it here as link to the sandbox.
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