ResourceRegistries 1.3 depends on changes to CMFCore/Skinnable.py in the
CMF 1.5.5 release. So for Plone 2.1.x install CMF 1.5.5.

To use with Plone 2.0.x, you have to make sure to move the header.pt
template from the 20compatibility directory to  skins/ResourceRegistries

But Plone 2.0.x uses CMF 1.4, so you need to patch CMFCore/Skinnable.py with the patch (or replacement Skinnable.py) from
http://plone.org/products/resourceregistries/documentation/how-to/plone-2.0-compatibility/