Zero Reserve Rules

This is a list of rules of the payment network:

Remote payments are the done by doing a series of friend to friend payments (hops) on a route through the network. The system tries to find the shortest route.
Remote payments carry a fee on each hop which that hop can set freely and which is subject to the market, not including the payer and the payee. This is to prevent the network to get spammed with bogus payments and also to provide an incentive to route payments. So a payment to a friend is free. A payment to a friend of a friend will cost you 0.2%, paid to your friend. And so on.
Debt carries an interest which you can set freely, greater or equal to 0%. We recommend that you do charge interest. Interest will be compounded daily.
You can dispatch a payment at any time, but completion requires both you and your friend to be on-line.
Payments are irrevocable, just like with cash or with Bitcoins.
Remote payments can be done only to an amount of smallest credit in all intermediate hops.

It is possible to edit the debt figures in your client - it is code under your control, after all. Your friend has the correct debt figure, however. So attempting to cheat that way is sure to create a conflict.
If you grant a credit in Bitcoin, be sure you know what you are doing. The Bitcoin price can go up at any time, to any amount. If that happens, your friend may be unable to live up to his obligations.
If your friend runs away with his debt, you are out of luck - Zero Reserve is not responsible for that and cannot help. Maybe your legal system helps you, maybe not. So grant credit to any given friend only to the amount you are prepared to lose.