This paper presents an open source implementation of a GNSS software receiver that targets Galileo E1B and E1C signals. After discussing the signal structure and the general architecture of the proposed software receiver, we provide detailed descriptions of the main signal processing algorithms involved in acquisition and tracking of such navigation signals. Experimental results with signals broadcast by in-orbit Galileo satellites validate the approach. The connection to external software (that allows in-the-loop testing of algorithms implemented in popular commercial tools) is also presented and validated with real-life signals.