Anybody can run pmcheck. There must, in this case, be a signature applying to the designated newsgroup or user. Without such a file, or if no specific newsgroup or user is given, all the signatures in the article are checked. In this case it is not considered an error if the signature cannot be checked due to a missing public key. These two scripts are used by pmapp and pmcheck to recreate the exact input for the signature, and to extract the list of newsgroups in the header, respectively.
More documentation is in their manual pages.
The PGP Moose checking daemon is packaged separately, as there would not seem to be a lot of value in having too many people running it. Accordingly, I was less precise in making it run absolutely everywhere. I expect it would be easy to interface it to CNews, but I don't have one. Mail is sent about any errant articles, and automatic cancellation may be enabled. The first allows a moderator to mail a PGP signed copy of the article to be posted.