Just recently I have the option to open source a credit card
processing application that is written in ruby using eventmachine.
This application processes cards directly to Vital.  It basically
replaces an online payment gateway.

On one hand I'd love to open source it, but on the other I'm hesitant
because of the potential for abuse or misuse given the growing body of
security requirements that go along with credit card processing.  I'm
also wondering if it would even get much use.

You have can have multiple copies of the application running that
share the same database (postgresql) for a certain level of fault
tolerance.  The client protocol is netstrings over tcp/ssl.

Thoughts, comments?