Yeah it is. It basically narrows the spec down a bit. For example, it has some specific classes like the dcat-us AccessRestriction class, but it also mandates the publisher of a catalog (collection of datasets), while vanilla DCAT has it as a recommended field.

In Europe, the EU promotes their own DCAT-AP profile a bit more. Same purpose, quite widely used actually by governments, but not completely compatible with DCAT-US even though both are extensions of DCAT. Fun fact, DCAT-AP v1 predates the standardization of regular DCAT v1, which led to some minor inconsistencies. In the subsequent versions that development process is a bit more aligned now.

> DCAT-US v3 is not a “new” standard; it is a “profile” of or implementation of the World Wide Web Consortium’s (W3C) DCAT standard.

It was hidden at the top of the list of bullet points in the readme.