Can a projector be connected to the Receiver unit?
Yes, there should be no problem with this.
However if you would like to simultaneously hear audio from a separate Audio processor, for example a home cinema system, please consider how the video and audio will be synchronised due to the System Latency latency of the HD streamer.
A common set-up is shown in the diagram below in this case the home cinema system will need to be capable of delaying the audio by approximately 500ms. Many Home Cinema systems have the ability add this delay so this should not be an issue. You will just need to fine tune how much delay in order to match the video and audio for your exact set up.