- I thought Firmata is out of date. Is that true? Does this library useful in a desktop program communicating over the serial port?
It's not out of date. It's simply not being supported (or visibly supported, I should say) for the Arduino. Anyway, the sending application needs to send data in the Firmata format. Is this something you know how to do?
2) The examples seem to have code developed in the Ardunio IDE that execute in the desktop under Windows. Is that true? If so, what do I do to make that work?
Which examples are you referring to? Applications developed in the Arduino IDE run on the Arduino, not on the PC.
- Is the "Processing" library useful for communications over the serial port?
The Processing application is. It's more than a library.