Charging money to use money...hmm it almost seems like a paradox.
I have some issues with it.
Because its main purpose throughout history has been to
take property and create slaves, it seems like there may be something that's "not right" about usury.
One problem is, money isn't really real. It's just a concept. And there are differing definitions of money, what makes good money, etc. I think part of the reason that usury is considered OK is this confusion over what money really is.
Since it helps to use metaphors or analogies to understand difficult concepts, I'll throw one out there for anyone who wants to take a crack at it:
If a person borrows a certain amount of "something" from you, how can you ask a person to bring back more of that thing than what you gave him in the first place?
Consider for a moment that we live in a barter system without any money. We are both farmers and I lend you my cow. Would you sign the contract if I required you to bring back more than one cow (charge interest)? You would probably think that was unfair. You'd say, "That's why I'm borrowing the friggin' cow in the first place you dummy! Because I don't have enough."
It doesn't make sense to make a person bring back more of the same thing he borrowed, does it? But that's what usury is.
What if it was something that is only useful if it is consumed, because that is true about money. Money isn't useful until you spend it. Food is only useful if you eat it, so maybe that is a good example.
Now here's where it really gets weird. Let's say I borrow 5 apples from you. It already seems weird, borrowing food? How can I do that? Once I eat those apples, they're gone. I can't return something that disappears when I use it and the whole point of borrowing is so I can use it.
On top of this, you decide to charge me interest in the forum of 1 apple a month for every month that I don't bring your 5 apples back. Now this is REALLY starting to sound like a raw deal. No thanks.
Back in middle school, kids always used to say, "Can I
borrow a piece of paper?" Sometimes I'd get smart and say, "Borrow? Are you gonna give it back when you're done?

"
They knew what I meant of course. They were going to use the paper and turn it in, so there's really no way I could expect them to give that same piece of paper back.
Borrowing a pencil is a different story though. You can get use out of it without destroying it. So you
can borrow a pencil.
*Can you get anything useful out of money without spending it?* Then how can you borrow it?
Based on those scenarios, here's my opinion:
It's not that usury is right or wrong
per se,
it's that no one in their right mind would agree to borrow money at interest if they really understood what they were agreeing to.