Here is the thread where I discussed it in more detail - see post #8 & #26
http://forums.overclockers.co.uk/showthread.php?t=18375212&highlight=usury+username_freakbro
As posters like Dolph were quite pejoratively vocal about (unfairly imo), they are still getting a return on investment, just that it is a different mechanism than 'interest'
But that is by the by, the more fundamental principle I was interested in with ethical banking is the premise of shared risk of the investment, where both the lender and borrower have an invested interest in the repayment of the loan.
This could help promote responsible lending, something our own system severely lacks.
There is no principle involved in the actual implementation of these things... they're just workarounds/loopholes so that Muslims who might feel guilty about having a bank account get to feel slightly less guilty.
looks like I was cynical about them in that thread too:
http://forums.overclockers.co.uk/showpost.php?p=21283035&postcount=31
with perhaps a better analogy too:
"It's like an escort claiming that she doesn't perform sex acts for money but rather her clients pay her for her time during which she might choose to have sex. In reality she's still a whore. "