You are, of course, free to use whatever term that you prefer. I have a child who is not willing to be identified by gender;
"Open marriage" is one kind of polyamory, because it is honest, responsible, and not monogamous. Pure swinging is not necessarily a polyamorous activity,
but the "emotionally involved friendships" are certainly included in the term.
Open marriage is not the equivalent of polyamory, because there are many
other kinds of polyamory as well. But it is one of the forms that polyamory
can take.
I offer these definitions with tongue firmly in cheek. ;-)
Kelly