As the primary author of the original SoftwareSerial library that ships with Arduino (and now with Galileo), I can tell you with some certainty that this won't work as-is on Galileo. There are quite a few dependencies on AVR in that code.
I'm not yet an expert on Galileo architecture, but given what I know, I have to wonder whether SoftwareSerial is even possible on the Galileo, the curious statement in the FAQ (https://communities.intel.com/message/207619) notwithstanding. If the fastest a general GPIO pin can toggle is ~230 Hz (see Re: I/O speeds?), then even 300 baud SoftwareSerial would seem out of the question, especially since the underlying OS is not real-time.
I would love to be contradicted on this point by the way, but I think we need to correct that FAQ.