I'm pretty sure than polygamy differs from communal living, in that a communal arrangement doesn't necessarily involve sex or marriage. When I was at uni, I shared a house with eight other people of assorted genders. While I can't say that there were no hook-ups (it was none of my business), but I never had sex with anyone in the house. But it was 'communal' in the truest sense of the word - we all shared resources and responsibilities to keep the house running.
Boru
Boru
‘But it does me no injury for my neighbour to say there are twenty gods or no gods. It neither picks my pocket nor breaks my leg.’ - Thomas Jefferson