The only place that mentions Claris in the software is in the Sample Movie included with the Quicktime Tools stack which is a short animation of the Claris logo. Even in the about box it says Apple and not Claris. I've never seen an Apple-branded Hypercard 2.1. I think Apple may have released 2.1 and probably 2.0 only under the Claris name because there's nothing unique about this version besides the Claris logo on the disks and manuals and in the sample movie. I've seen Apple versions of 1.x.x, 2.2, 2.3, and 2.4, but never 2.0 or 2.1. The "Development Kit" in the name seems to have no special meaning.