Skins donations for MU Online servers

Nothing. The donation module is free to download and use. SkinsFlow charges 2.5% of each payment credited to your balance, and nothing else: no setup fee, no monthly fee, no minimum volume. Failed, expired and returned payments cost nothing.

Any files that keep the shop currency in a database column. You point the module at the table and column in its settings.

Steam can hold traded items for up to 7 days and return them to the customer in that window. A protected payment is not counted as paid yet: the currency is credited when the hold ends. When the hold ends the payment completes on its own, or you can release it early in your SkinsFlow dashboard if you trust the customer.

By default the module waits until the account is offline, because many server files overwrite the currency on logout. It credits automatically after logout. You can turn this off if your files read the database live.

Yes, when players receive something in return, such as cash shop currency. You need the right to run your server and sell what you offer.

Yes. Turn on test mode and use your project's test secret. The checkout then shows real items with real prices but no item and no money moves, and buttons let you play every outcome: paid, protected, returned, declined. Use a test account to check delivery.