If you’re looking for a free credit card processing system, you may want to check out FreeCCS from Semaphore Corp..
It will work on any Mac running System 7 or later versions (though it’s not been Carbonized for Mac OS X). You’ll also need a modem that recognizes “AT” commands and is capable of running at 1200 baud (any currently-selling modem will do) and a valid credit card merchant account with access to the MAPP (MasterCard Automated Point of sale Program) credit card network (or a MAPP-compatible network). MAPP is a general purpose bank processing network supporting a variety of credit cards, not just MasterCard transactions.
If you’re not a merchant authorized by your bank to perform credit card transactions via a MAPP-compatible network, you won’t be able to use FreeCCS.
The freeware product is made available on an “as is” basis only. It’s designed for experienced merchants who are already successfully processing credit card transactions. The product was created because of problems encountered with a commercial credit card package.