If for some reason I were invited to Foo Camp, and for some reason I were to have a spouse, would I be allowed to bring them?

Probably not. But you can make the case. For example, synthetic biologist Drew Endy asked if he could bring Christina Smolke, his SO, who is a fascinating scientist in her own right -- doing fascinating work with RNA -- so we of course said yes. This is one of those emerging areas where we want to know more people, so having Drew + Christina was a big win for us.

But basically, it's too crowded as is. We're sorry, but we just can't afford additional folks.

We have thought about whether it would make sense to set up some parallel activities and a place for families to hang out, though.

But unfortunately, facilities are limited, and there is a cost to these things. And since this is a free event, there's no subsidy :-)