Actually, the words "open source" are a recent addition to our header, whereas we've always had the github link. We discovered from feedback that many people who visited our page had no idea that it was open source, since most people don't look at nav bars, and this of course completely changed their perception of the project (for the worse, obviously). When we put "open source" into the header, we saw a marked increase in interest.

Thanks for the feedback, though! We'll think about inserting "app" in there.