I attempted to create a second Forum, and it said:
"A forum already exists with your e-mail...
You can create only one forum with your e-mail,
but you can moderate several of them.
See it with other administrators."

I conclude that the "One Forum per email" is a rule is so that they don't give free forums left and right, but I found some of this unclear.
Does "but you can moderate several of them" merely mean that you can be a Moderator on multiple Forums?
And what does "See it with other administrators." mean?

Yes you can moderate as many forums as you like with that email address as that isn't your forum.

Only one email address per forum creation. You can register with the same email address on different forums.

SLGray wrote:Only one email address per forum creation.  You can register with the same email address on different forums.

But if you want to create a second forum,you will have to create another account using another email address. Which will be a different account from your first account, different founder name and everything.