No, they mean _outside_ of marriage and not specifically _inside_ any other framework. What we call "concubinage": people living together without being contractually engaged to each other. The PACS is marginal here and would mostly affect first people who _can't_ get married. Concubinage does not mean you can't share parenthood or loans etc. It just means you can get much benefits from the situation (you mostly get to pay more taxes, you have less or no rights on inheritance etc.)
> If so, "outside marriage" seems like a comparative misnomer. A
> French friend in her 60s introducted me to someone who had 6
> brothers and sisters, none of them married. But further
> conversation revealed that 5 of them were in monogamous
> relationships that had lasted more 15 years, given rise to
> children, and where they owned houses jointly. And where, if they
> want to leave each other to make a pacte with someone else, they'll
> need lawyers.
The PACS has not been here for 15 years :) Most probably, the people you mention have just been living together for all this time, without a "contractual" link between them.
> The difference between marriage and a pacte seems more equivalent
> to the difference between a marriage in church and a marriage at
> the justice of the peace than between marriage and what we in
> America would call cohabitation.
Well, I don't know what is tha law in the US but in France a marriage is _exclusively_ a civil contract between two individuals and with the representant of the State as a third party "witness". There is nothing as a legally binding religious marriage. So there is A class marriage and B class PACS, both are civil contracts. The only difference is the requirements to contract and the benefits.
JC