I’m not sure I would consider that a red flag for this particular project. Both RSS and NetNewsWire are very mature, they’ve been around for about twenty years.
I suspect you may know this, but for the sake of others reading the comments, this "version" of NetNewsWire started from the original developer of NetNewsWire (Brent Simmons). NetNewsWire had passed through two other owners and the final owner (BlackPixel) returned the brand back to Brent Simmons who had already started a new, open source RSS reader which has since been known as NetNewsWire 5 (but doesn't share code with the previous versions).
