Reply To: connect two arduinos?
Including the library you found is not going to work simply by including it in the sketch. You need to write a wrapper so that Firmata understands how to communicate with that library. This is not so easy. You can find examples in the custom_examples directory: https://github.com/soundanalogous/Breakout/tree/master/custom_examples. Basically look at how the RFID library wrapper works in those examples. You’d have to do something similar to get the Servo library to work.
Likewise, you can’t pass arbitrary assignments such as “x = 12” through Firmata since Firmata doesn’t know what to do with the value. You need to extend StandardFirmata to understand such things, much like in the custom examples I linked to above.